­Spawnsire of Ulamog is one of those few cards that interact with your sideboard giving the card an alien feel. I wanted to design an Eldrazi that captured that alien feel. I chose the ability to have this card give a you a different Eldrazi if countered was in line with Kozilek's abilities of messing with perceptions. Sine the card needs something else I originally gave it trample for the body, but then I switched to menace. While the word "menace" doesn't fit (any better than it would for any large eldrazi) the idea of needing two creatures to block it comes off to me as it takes two people to figure out what exactly this thing is when trying to fight it.