A narrow card that is hard to abuse yet incredibly powerful
Ice Age introduced us to Brainstorm, a card that now dominates in any format its legal in, but before that, there were some competitive decks that began to understand the true power of drawing cards
Essentially, if you have a full party with all four of these on the board, you can pay one white, one blue, and one black mana to give the Warrior lifelink, deathtouch, and make him unblockable (deathtouch and unblockable at the same time has no real use, but thats still OP to think about)
The other interesting aspect of coven is that it demands you commit to the board fairly significantly to see any results
Black Rob Lucci is a control deck that relies on 4-cost Rob Lucci as its main removal option
Returning Mechanic: Energy Sometimes, mana just isn't enough to fuel your needs