Wish Stone

The Wish Stone is a sentient stone which grants wishes, typically at the price of the wisher's masculinity.

In Archer
When Myro finally managed to hit the bullseye in his makeshift archery field after a year's practice, a Wish Stone presented itself to him. It granted his two wishes to become an elf and an expert archer, and in return took his masculinity, turning him into Myra. She didn't seem to mind.

In Contentment
"'I will grant it anyway, and change a bit more in an effort to achieve your intent.' - the Wish Stone on Zyran's wish to be rich"