Mythical creatures skin set?

just got the idea but why is there not a mythical creatures skin set for example Centaur Hecarim Satyr Varus Mermaid Nami Phoenix Annivia (fire shes technically an ice phoenix) Pegasus Hecarim Pixie Ezreal Banshee morgana/syndra/maybe Cassiopeia Bigfoot Braum Blackeyed Annie Bogle Fiddlesticks Bogeyman Tham Kench Cyclops Garen Imp Teemo Manticore Reksia (this ones a Big what if cus her kit doesnt match the mythical being) Typhon Malphite Wendigo Yorick wraith Karthus

please give more ideas in the comments id like to know what others can think up