If you want a video version of this, it is here https://youtu.be/VoiJap6MUTQ
In dungeons and dragons, and high fantasy tabletop games in general, player characters gain power far beyond that of the average human or elf or orc. But such power always has a limit, which for dungeons and dragons 5th edition, is reaching level 20. Why can’t characters go beyond that? Mechanically it makes sense, a game needs to bound the power level somehow, otherwise Wizards of the Coast would have to make an infinite number of abilities for each class. And a character at level 20 is already on par with a demi-god, so going much further would risk the mechanics of the system collapsing. So mechanically level 20 makes sense, but why narratively do characters never reach level 21?
I want to give you some inspiration on how to handle that and discuss your characters end point with your DM. This may never come up for your characters specifically (rip scheduling a long term game), but it can also explain why the heroes that came before you are not solving the problems you run into. And maybe your DM will even let you make some these old adventures for you to find in the campaign! Before I start, aging is of course a reason for all heroes to someday stop fighting. But since elves can live hundreds of years, and war forged indefinitely, these heroes could be walking around for a long long time before their age gets the best of them and I think there are more interesting reasons for adventures to stop…well adventuring. So without further ado, let’s jump into reasoning for each class. BARBARIANS
Barbarians are martial warriors, that draw their power from rage. This is noted as a “primal ferocity” in the players handbook, in which a barbarian erupts into a state of intense violence to survive what which would kill others and land blows with excruciating force. A barbarian will burst into this state of rage dozens if not hundreds of times throughout their adventuring career. With each instance only ending if the barbarian has no more enemies to cut down, or wounds to whether. A barbarian’s rage could come from many places but is always fed by a cycle of violence and death. But what if they become numb to this cycle? They may burst into rage, only to find they feel nothing for those they slay, and no pain when a new line of red is drawn from them, for it sits in a sea of scares. And soon thereafter, the rage never starts in the first place. They let their emotions flow out for so long, so intensely, that all that is left is calm. They are finally free of the rage that clung to their heart for years.
This is the end I envision for Barbarians. Not one of slaughter and death, but of calm and self-reflection. Some would return to their tribe of origin, doing the simple tasks of a simple life and finding comfort and fulfillment in them. Maybe their past will one day come for them to continue the cycle of violence they abided by for so long ago. Maybe a young group of adventures will find them alone in a remote mountain home, seeking the answers to questions that were buried with the old one’s rage. No matter what, this barbarian cannot bring themselves to the ferocity they once felt. Instead they build and cherish a life centered on fostering growth, where in the past they caused destruction. BARDS
For bards, I see them having two possible ends when they reach the height of their power, They either go the way of the Rockstar, where they live fast and die young, or become so astounding that the heavens above take notice. First the Rockstar. As you may know, substance abuse is a big topic of discussion in the entertainment community of the real world, and the fantasy world probably has much more powerful and dangerous drugs to choose from. Perhaps it is not a simple overdose after a life of substance abuse that does in the Rockstar bard, but a cocktail of potions that makes them forever in a gaseous form or reduces them to the size of a flea. No matter what, the bard went a step too far in the chase for an ever more difficult to reach high.
If a world-famous bard is not the type to party with dangers levels of intoxication, instead their legendary performances could charm the very gods. After one truly beautiful performance, an angel may arrive to take the bard to Mount Celestia, so that they may enrapture the gods just as they did the denizens of the material plane. If rejected, the gods that follow law may abide by the bard’s decision, others may not. Demons and devils may soon hunt the bard across the planes, for Asmodeus wants a minstrel for his demonic court. Either willing or unwilling, the bard will come to live in the outer planes, far from the troubles of the material plane. CLERIC
Speaking of the outer planes, that is where a powerful cleric will end up, as they ascend beyond mortality. To receive an ever-increasing wealth of divine power, a cleric must exemplify some tenant of the god they worship. As they are granted power, and show they are worthy of it, they exemplify that tenant or set of tenants so much that they become a living saint. With this rise to sainthood, they must travel to their god’s domain and serve them there, for a saint has much work to do and faithful to shepherd. The cleric will be able to provide mortals of the material plane blessings or boons, but they will be given over a long time and over a vast array of people. Thus it will seem in any moment on the material plane to be of little consequence. DRUID
Druids will have a similar ascension as to clerics, but instead of ascending into the domain of a god to bless the faithful, a druid will ascend into a force of nature, forever more protecting their domain on the material plane. Druids are in tune with nature, that is how they learn to become beasts to protect themselves and cast spells which provide for others. The more powerful the druid, the more powerful the beast they can become to protect the natural world. Until one day, the druid becomes powerful enough to transcend melding into simple beasts, and instead becomes a force of nature. Perhaps they will become a great tree, whose roots sink deep and feel the forest for miles, searching for threats and animals in need. A tree with branches and burrows to hide the young as they grow and thrash any who would harm the forest. A guardian that has become one with that which they protect. And a guide for those lost in its woods. FIGHTER
A fighter will be ravaged by time much more easily than most of the other classes. For it takes intense physical training and martial discipline to reach the peak of fighting capabilities. Maybe there is a limit that cannot be passed for such things. For youth lacks experience, and age lacks vigor. However even a fighter years from losing their youthful edge may find themselves with shifting priorities. Instead of facing an enemy as one, a world renown fighter can become a teacher and a leader, so they may face that same enemy as one of ten thousand. Rising to generalship means a focus on battle strategy and communication. The fighter will still find themselves drawing their sword, but far more often they are training others and learning to lead. As they sharpen their strategic vision, they’re sword dulls. MONK
Monks, much like fighters gain power from honing their body. Unlike fighters they also hone their spirit to harness the ki that flows through them and all living things. A monk’s greatest weapon to hone themselves is mediation. But mediation is a calm slow process and it can take centuries for one to truly understand the full extent of their body and spirit. Especially as both continually change. To achieve full understanding of one’s self and become enlightened, a monk’s best option is to use astral projection
to meditate within the astral plane and its sea of nothing. For there in the infinite nothing, all one has is the self. And in the Astral plane, a thousand years is but a day in the material plane, allowing for deep and lengthy meditation. The body left behind craves not for food or rest or air, suspended as the monk floats beyond themselves. Thus, every crease of the skin, every drop of blood in the veins, and every single cell of the body can be known and felt. As can every aspect of the spirit. This meditation can be salvation, or ruin. For in the astral plane lies dreadnoughts, beings before time made to consume those that walk the plane between planes. A monk deep in meditation may never see the beast push through the infinite gray void towards them. If the monster severs their silver cord, the monk’s spirit splits from their body and they die. If consumed by a dreadnought, its donjon will be the monk’s prison until death.
If a monk avoids such a gruesome fate, then they can reach true enlightenment and understand the connection they have to the world, the planes, the universe, everything. When they return to their body, wherever that may be, it dissipates, for a body is of no use to them now. Instead they spread their ki into all beings, be they, plant or animal, devil or demon, god or man, and blanket the universe with a small shard of themselves. The ki of a single body is miniscule on the cosmic scale but spread throughout all of space and the rest of time, it alters the rhythm of the universe and the shape of the future forever. PALADIN
A paladin’s focus on the self is different than a monk’s. For it is only half of the whole. “A paladin’s power comes as much from a commitment to justice itself as it does from a god.” The end to a paladin should follow these words, for good or for ill. A paladin’s commitments may come to symbolize the tenants of the god they follow. And when their power is unmatched on the material plane, they are beckoned by their god to enter the domain of the divine and become a warrior angel, fighting forever more against the demons and devils that cause so much injustice throughout the planes. Perhaps a cleric, in a time of need, will call out to their god and this paladin will be their answer. A holy warrior, clad in light, come to defend the tenets they upheld in life. Or perhaps a paladin falls from grace, as is so easy to do for others, and breaks their oath. This is a difficult thing for a paladin do, since a paladin’s oath is tied to the deepest held beliefs they have. To break such an oath requires immense stress, trauma, or deception. No matter the cause, a paladin that does not hold firm to their oath is but a normal soldier, and that is all they will by from then on.
The final possibility for a paladin is that they no longer need to uphold their oath, for the oath has been completed. Vengeance has been done, the darkness has been dispatched, the world is finally at peace. No matter the cause, the paladin’s success releases them of their power, for they need it no longer. In the next time of need, let another don the mantle of courage and become a holy knight. This paladin shall rest. And when their final days come, they will look back and know, they triumphed over the forces of evil. RANGER
Rangers may not be so lucky. They must protect against an endless horde of monsters causing destruction in the material plane and the planes beyond. For every beast killed as it rampages through a village, for every monstrosity put down before it can consume another victim, for every demon banished from the realms of men, another will take its place. Yet a ranger lives on fighting against this inevitable truth if only to delay it another day. That inevitable truth will lead to a ranger’s inevitable end. Whether the monsters wear down a ranger, or if time does, it does not matter. Eventually they’ll lie dead in the place they tried to protect, as monsters roam past. Striking into civilization or tearing through the forests, until another ranger rises to slay them. ROGUE
Just as the ranger fell to the endless horde of monsters, the rogue shall fall to the endless cruelty of their fellow man. A rogue learns early to steal, cheat, and kill. Whether to simply survive a helpless situation or claw their ways to the top is irrelevant, they will always incur a debt from such things. A debt that can only be paid in blood. A rogue at the top of a criminal organization will find themselves a target for rival factions and the ambitious among their own ranks. An assassin rogue may tie up all the loose ends for a mission, only to find themselves as the last end needing tying. Even those that escape such life traps will have their past sneak up on them one day, just as they have so easily snuck up on others a hundred times before. The world of a rogue is dog-eat-dog, and some day they will be devoured. SORCERER
A sorcerer is much more likely to be devoured by their own power than an outside threat. Though depending on the source of their power, this may be welcomed. Divine, Draconic, and Storm sorcerers allow their mortal forms to be consumed, for it leads them to assume another, more powerful state of being. Those of a divine soul may become a demigod and even a true god with enough time, ascending above the troubles of mortals. A draconic bloodline sorcerer fully unleashes the power within their veins and transforms into a dragon. With this transformation comes immense power, but also ego and an intoxication with one’s own nobility. Sorcerer’s of the storm become the heart of their own never-ending tempest of rain and lightning. They float above the land as all storms do, detached from what is below but affecting it nonetheless.
Sorcerers of Wild Magics and Shadow Magics are not so willing to give in to their power. A wild magic sorcerer is forever on the precipice of annihilation, be it of their enemies, their allies, or themselves. Without meaning, they may tear open the spaces between the planes, flooding the material world with what lies beyond. Or erupt in an inferno, engulfing the city streets around them. For fear of these outcomes, they may be hunted, by man and god alike. Or they may resolve themselves to never use their magics again, for fear they will become the destruction they once protected the world from. Shadow magic sorcerers on the other hand, may limit their use of magics to stem the tide of darkness growing within them. Each spell they cast pulls from the dark energy of the Shadowfell, which in turn allows that energy to cling tighter to the sorcerer. In the darkest night, shadows may creep into the very heart of such a sorcerer, turning it pale black and lifeless. This fate may be halted if such a sorcerer spends their days in the Feywilds, a place filled with energy in direct opposition to the shadows in their heart. But there they must remain forever, least the shadows crawl any deeper. WARLOCK
Warlocks have the opposite problem of sorcerers, for their own power may not devour them, but that which gifts those powers, their patron, just might. Each time a patron gives a warlock power, there is a chance the warlock has become powerful enough to oppose their patron. Perhaps giving out such power is worth the risk, for the warlock is close to completing some goal of the patron. If the patron cannot stand a warlock retaining these gifts, then they will come to conflict, for a warlock will not want to relinquish that which they have gained. This will only end with either the warlock or their patron destroyed. If the warlock survives the conflict, they can take up the mantel of patron, and give to others what they once yearned for. As this power is given, they will know it could mean their end if given too freely. WIZARD
The downfall of a wizard is similar to that of a warlock, as it requires them gaining the power, they sought for so long. With their endless study of the arcane, wizards hope to reach spells that the mind is too mortal to contain. For these magics are only fit for gods to wield. A wizard or sorcerer at the height of their power can bend reality to their wishes, imprison the greatest evils for millennia, and rain hellfire for miles. Sorcerers avoid the dangers of containing such magic by either becoming something beyond mortal or succumbing to their powers before it can affect them. Wizards have no such respite and their mind can only hold for so long. Eventually the mind buckles under the strain of holding such immense magical glyphs, incantations, and energy. As it does, a wizard’s most prized possession, their mind, becomes the prison in which they cannot escape. Recent memories become a haze of forgotten shapes and faces. Conversations held moments ago disappear like mist. The process cannot be stopped, even if all spells are forgotten. The mind has been cracked and it will flow out. As memories fade and the world becomes a land of mysteries, the mind spurts, gasping for thought. And from these gasps come some of the magic held deepest and longest. Balls of fire erupt without word, magical barriers are erected with mundane gestures, and darts of magical energy strike friend and foe at random. The danger such a wizard possesses to nearby civilization will cause harsh measures to be taken. If a wizard afflicted by arcane dementia survives the assassins and blood thirsty mobs, they only have a life of deteriorating mental function left ahead. This is what makes so many powerful wizards seek out lichdom. Not only does becoming a lich give them a reprieve from death, but also ensures they can wield their immense arcane power for centuries instead of years. CONCLUSION
With that, every class of hero is limited for a reason. Some are limited by their focus shifting away from themselves to leading those that have gathered around them. And with this there is always the chance of betrayal ending life prematurely. Others will find themselves consumed by the power they once wielded for so long, a raging inferno that can no longer be contained. Yet others still will be consumed by their power in such a way as to be reborn. But this new form will care little for the wants and needs of the mortal that came before. Perhaps the best off are those heroes that simply stop fighting. Instead they live into old age following mundane patterns to carry out mundane tasks and finding comfort in them. No matter the hero and their end, they will be remembered. For one cannot become legendary without first becoming a legend.
Hope this gives you some character inspiration!