New Character Classes
Instead of a righteous, divine paladin or crusader type, I would love to see a grimmer, darker take on a priest or cleric archetype. They might be a fearful, lost pilgrim wandering Sanctuary, hanging dearly onto their last threads of life. Or, a stoic death-seeker following the dying religion of a two-faced god-hero of old. Perhaps they are a warrior poet of sorts, but one that only sings tragic tales of flawed and fallen heroes and false martyrs.
Alternatively, they are a wounded fallen angel who has long since abandoned aspirations of ever fully healing—let alone re-ascension—and see their strive for a sense of purpose as folly, a sick joke they can't help but play on themselves.
A dirty-fighting urchin from a large city, a roguish scoundrel and grave robber who has been traveling around the world their entire life, or a former pirate lord who has forsaken their mutinous crew and seeks treasure in new parts of the world. Over time they might grow to become a great duelist or battlefield tactician, if they can resist their curse of greed.
An archaeologist-wizard who discovered an ancient power in the desert around their home. They left the desert to escape the horrors they witnessed, and look for other artifacts and lost knowledge that might bring peace to their mind, or at least occupy their curiosity (obsession) and give them short-term purpose in fighting demons. Perhaps they are instead an illusionist or psychic who summons living nightmares from their own mind and cripples the minds of others. Or, a warlock and servant of a distant star who calls unknowable things from the cosmos to Sanctuary.
A twist on the necromancer as a cunning and sneaky curse mage (witch/warlock) who isn't afraid to use their enemies' tactics and forbidden knowledge against them and actually relishes it. They aren't unfamiliar with old ways of healing thanks to their parents' teachings—their darker fascinations are thanks to their parents' supportiveness of their morbid curiosity as a child. Perhaps they are a child of a human and a fiend.
Instead of a monk or another fighter archetype, an opportunistic survivalist who has trained in multiple fighting styles/stances and the use of intricate traps and explosive devices. They might be a ranger specializing in two-weapon fighting, a scavenger who prefers to fight from afar, or a tamer of beasts that hungers for demonic flesh as much as themselves (figuratively or literally).
An old mystic with a greatsword possessed by their only surviving friend: a fiend wreathed in ever-burning, tortuous fire. Either the enchantress from Diablo 3, somehow still surviving and able to fight, or her child/grandchild carrying Maximus—the demon may have been transferred from the weapon to their mind and body. Or, a devout follower of a perverted faith based once upon a time on the life story, deeds, and teachings of the enchantress, and who is consumed by lunacy over time.
An artificial golem who woke up in a hermit's workshop or the depths of a sage's bizarre pocket dimension. They are either an engineer who augments their metallic body and the weapons and armor of their allies or devices they deploy, or an alchemist who concocts unstable potions and steals essence from their enemies to infuse into their alien heart.
Alternatively, they are a mutant zombie alchemist who uses their bizarre infusions and skeletal grafts to keep their body alive and to turn it into a living weapon. Or, a rotting, resurrected agender mummy and former archivist-wizard whose cursed, shriveled, black heart-phylactery exudes strange energy, or a golemancer/lithomancer lich with an artificial black iron heart-phylactery. (They could also be the archaeologist described above.)
And no class would be complete without...
Legendary and Set Items
Druid: Permanent cursed/diseased-looking inhuman form, or all their transformations are extended and turns their focus to melee. A fey form emphasizing nature, death, and disease, or that of a dark dryad that makes them transform into beasts made of shifting plants that glow inside with eerie green light or swirl with dark shadows. Runestone armor crackling with electricity, with transformations of stone or pure lightning that call down lightning bolts.
Sorcerer: Blue-white armor made by unseelie fey that allows them to become an icy archon. A dress of fine, dark or light purple cloths and thorny silver jewelry inspired by insects, all infused with and oozing unseelie magic. A crown of elements that can be triggered by casting elements of one type, and summons a fiery skeleton, storm spirit, or ice banshee. Armor made from a butchered phoenix.
Barbarian: Patchwork, treated demon skins that fill them with demonic blood and fury when raging. Iron or stone golem weapon, or chest armor made of the belly of a smelter demon or forge of war. Bloodthorn dryad weapons. Runestone plate armor or barkskin and enchanted tattoos that turn them into a furiously growing storm while whirlwinding.
Cleric/Necromancer: A skeletal/phantom mage that can temporarily walk the realm of the dead. Armor that turns them into a white-hot skeleton bound in spiked black iron chains or welded into spiked, smoldering black plate armor. A veiled spirit or blood angel. The form of a vampire themed to a new place/culture in Sanctuary.
Whether or not any of these ideas are seen by the team, hopefully they
can inspire you to make your own characters and classes and items for D&D, be it for a
game of "D&Diablo" or other adventures in settings like Dark Sun, Ravnica, Planescape, Spelljammer, and Innistrad.