It gives lifegain on entry triggers and rewards you with card draw once you hit the life threshold, so routine board development keeps paying you back
It may also create some new lists that play differently than the rest
Coven demands more setup than it may seem and the payoff to set this up and get an attack off without an opponent removing something is lackluster
Casting Cost: Card Text: At the beginning of your upkeep, if an opponent controls three or more creatures, sacrifice Defense of the Heart, search your library for up to two creature cards, put those cards onto the battlefield, then shuffle
First, in the hands of Randy Buehler at Pro Tour Chicago, and then when piloted by Andre Konstanczer, Necro-ing up Knight of Stromgald, Sedge Troll, and Sengir Vampire, while other folks in the top 8 were untapping their Tolarian Academy with Time Spiral
Picture this: a card that gives you three life for every 2 mana you pay