Dragonflies
Every dragon dreams of being a dragonfly. They dream of shedding their cumbersome greed and terrible fire. To flit in iridescent bodies unburdened by teeth or claws or horns. To glide on delicate wings where their shadows once brought terror.
Dragonflies leave behind the hoards they amassed as dragons. It is their one regret, however small.
Undergoing the metamorphosis that reduces a dragon's form to that of a dragonfly also compresses all of their magic. A dragonfly can only be captured by certain powerful spells. A creature must already be of an Evil alignment to cast such a spell.
Each dragonfly can cast Wish once, after which their bodies become dull. Dragonflies have no wishes of their own that need granting. A dragonfly will never discuss the possibility of granting a wish unless asked directly by one they consider virtuous. But no dragonfly has a way of assuring the virtue of a petitioner.
Still ashamed of their past life, a dragonfly will never willingly enter the presence of a unicorn.