At the very least, if you time your Spike Cannibal right, you should get decent value for mana
When transformed, this turns into spellslinging paradise
Either you need to keep your hand intact or you need your discard spell to nail a threat and not let them take it with theirs
Many Allies reward you with some kind of trigger whenever they or another Ally enters, and what better way to take advantage of these effects than by doubling them
Domain is not structurally favored against any of the top 3 decksIzzet, Omniscience, or Mono-Red
Incredibly flexible and no mana cost to activate, Astral Slide lets you remove blockers for you and your opponents, stops attackers from hitting you, and of course, lets you blink your own creatures to re-use their ETB triggers and grant them pseudo-vigilance