According to official rulings, this is a perfectly legal way to resolve the card effect
Duke.Fleed on Modern Prismatic Slivers 8 years ago The deck still has some illegal cards (Brood Sliver, Clot Sliver, and Mnemonic Sliver) Also, some important cards for your five color deck would be some five color lands like Unclaimed Territory/Cavern of Souls or Gemstone Mine/Tendo Ice Bridge/Aether Hub
but if you're feeling ok with your colorfixing then perhaps it's ok :) You have a LOT of 3+ CMC ramp, I would suggest Nature's Lore+Arcane Signet in exchange for Migration Path, and Kodama's Reach (can't have Ishi-Ishi, Akki Crackshot pinging you ;D)
Exalted Flamer of Tzeentch Exalted Flamer of Tzeentch feeds the flames and fuels your hand each of your turns, while helping you burn your foes down
The face commander Ashling, the Limitless wants to focus on Evoke, while the alternate commander Mass of Mysteries wants to focus on Myriad
I can block it with [c]Karmic Guide[/c], which has protection from black