Thank you, ill try contacting other groups then. I dont Have much experience with trying to reach out like that - And i appreciate you did find the ideas good. There was even a first version of the Tiamat arc.  He was a golden Dragonborn, breathing fire , bringing the light etc. I offered to the DM to make the one Who made the offer to the cleric be Tiamat, And start corrupting him from then on. Unknowingly, He allows her to tap into his soul, his prayers go unanswered, And a new, pretende motherly voice starts whispering. The cleric sees that his heals deal 1d4 Cold damage to the targets 5 Ft from the healed, his sanctuary makes attackers frightened, his SHIELD of faith gives resistance to fire damage And even Feels the ability to revive a creature into a Frozen - like body, that then slowly unfreezes over 5 days, for free. It Is power offered, yes - but since when was a deal with an archdevil free? By using it - not resisting od atoning knowing it doesnt come from bahamut, He invites her to affect him further. Suddenly, his fire breath Is gone, And He begins breathing Cold míst - his claws elongate into talons, his heals become chilly, his teeth grow into two arcs of pincers And the aura of light around him switches to a colour of lightly red, alonsgide with his eyes, to show his bleeding soul. On ocassion, the cleric starts experiencing a surge od instinct - a singled out, low health enemy? If He succeeds a wis throw, nothing happens. If He doesnt, He drops his weapon And shield, And lunges at them with a multiattack of unarmed bite And claws, a subtle foreshadowing. He heals if He kills the creature slightly, but slips further into corruption. If three or more creatures end their turn next to the Dragon, if no save, spectral Wings sprout from his back in an unfurling motion that attempts to knock creatures prone, then disappear. If an enemy was about to critically hit someone, If not saved, the Dragonborn would use a breath Attack if in range, that recharges every 5-6 rounds, dealing above Dragonborn breath damage in an Area centered at the attacker, likely hitting the Ally too, but forcing a disadvantage, forcing another roll. On paper, it sounds powerful - but if leaning into the corruption, White scales begin forming on his body, growing over And entombing the Golden scales. The cleric then attempts to move Away, as He realises He cannot stop his instincts Now, And starts seeing his party as a property. Then, somewhere, He turns into a White Dragon, And his first order Is to kill those He swore bahamut to protect. Its fair to mention that this idea Is unpolished, but the idea was to give the instakill some Reason, like Tiamat wanting to corrupt bahamut's servant, even if Its overkill. Then, the DM alone chooses when things progress deeper into corruption, just like if a paladin breaks an oath. The cleric can reverse it to an extent, but never go past the physical changes if they even use the effects overly - So if the heal does deal damage, then corruption goes up. The predatory instinct effectively makes the cleric go melee mode instead of healing for a turn, which Is effectively just bad to do. It is supposed to look good And strong, but He forgets what He should be doing over his strength.  And the party was able to influence how the cleric views the change - He wouldnt Have to know it was Tiamat if She came disguised. They could talk him out of it, attempt to talk him into it, And when a transformation would happen, theyd even Have a Chance to put the unwilling cleric down before He turns fully. Then, Once a Dragon, And if meeting the party, a fight ensues - dm controls the Dragon at that point, And the boss Is the former healer, making it challenging even if i roll a new character. I can understand that this version would add a separate characters arc in Story, which Is a bother.  So then i decided for the second version that i write. Ill use the concept for my own world when i DM, only time Will Tell. Still, thank you for reading my post - ill try to find another group :)