It felt odd to make Ravnica a single color because it's so iconic for being a two-color plane, but if we chose any one of the two-color pairs, it would feel like we were prioritizing one guild over another
Split cards started out as two monocolour spells (colour A and B), then we got two multicolour spells with a common colour (AB and AC), then we got two of the same colour (A and A), then we got a return to multicolour splits again (AB and AC once more), then we got monocolour spells where you could only cast one side from the graveyard, one from the hand (so A then B)
The Emissary can find zombies but you have to pay extra mana to flip them and you lose the EtB effect of them as well which greatly reduces the value of a couple of the more top end ones
If you dont see classics like Relentless Dead, Grimgrin, Corpse-Born, Sedris, the Traitor King, or Phyrexian Delver here, its because I truly dont believe theyre better than the 50 entries Ive included
Enchantment Crawling Infestation At the beginning of your upkeep, you may mill two cards