Scavenging Terror

At the beginning of combat on your turn, if an opponent owns more cards in exile than the number of +1/+1 counters on Scavenging Terror, put a +1/+1 counter on Scavenging Terror.
At the beginning of each upkeep, if a player cast two or more spells last turn, transform Scavenging Terror.
"... While Emrakul sustains."