You can run Keruga in a Simic deck or in any three, four or five-color deck that includes green and blue
To meet the WUBRG requirements, you will have to use the Heroes in a Half Shell card, or you can use Leonardo, the Balance , and pair it up with one of the other Commanders that features the Character Select ability, which is a variation of partner
Devotion means counting up each colour pip (in the case of black, the skull symbols at the top right-hand side of our permanents) and adding up the total
Theres also two lore if you use her to quest
Mutavault on the other hand is only a 2/2, but satisfies the good and cheap part by being only one mana to activate
When enchanted creature dies, if that creature was a Horror, return this card to its owner's hand