Many Commander players like to build a piece of their identity into their decks, but achieving that can be difficult, especially for newer or more inexperienced brewers
Ashling, the Limitless, uses evoke to get big creatures out cheaper, and when they're sacrificed because of it, you can create a copy that costs you mana to keep around
Kefka's abilities make him just as deliciously diabolical in play on the board as he is in Final Fantasy VI , able to force players to discard cards all while allowing you to draw an equal amount, quickly getting enough mana to transform him into Kefka, Ruler of Ruin, getting ever closer to your win condition
If an opponent kills your creature before the ability resolves, then you don't get the effect and lose all the mana you put into it
A starlight rare version of Eia the Water Charmer, Gentle, can be found in the Eternity Code set
7: Destroy all non-Dragon creatures