This all starts with the sets major new mechanics, specifically the iconic Final Fantasy job system
She continues to scale as more lands enter the battlefield, and left unchecked, will frequently win games in a turn or two
Karn, Silver Golem, Masticore, Memory Jar, and Mox Diamond in From the Vault: Relics
Sephiroth on the other hand plays into the usual control strategies favored by Blue/Black by growing in strength for every opposing creature you remove from play
If youre fond of the type of gameplay that Alesha, Who Smiles at Death promotes, youll probably love Terra, and its reanimation ability even pushed up to 3 power instead of 2
The life loss of these two cards happens only if the mana is needed immediately, while the effect of each is very powerful