Aarthaxies - Fate's End

Aarthaxies — born of Tiamat’s will and carved from winter’s cruelty. He was a weapon with wings, simple and savage. But the pact he never meant to
make changed him. Now, something darker whispers beneath his scales. Terrorshade coils in his soul, fusing devil’s cunning with draconic instinct.
He tells himself he's applying Tiamat's will. But the truth? Murder feels too good to question.

While in his lair - whenever an enemy rolls a death save and fails, deal one extra damage die.