It was Invasion block in the Standard format and I was using Spectral Lynx and Sengir Vampire as my main creatures
for example, your cool counterspell should be blue, your hasty creature is likely red, a card that cares about power is green, and so on
This helps free up inventory space while gaining valuable new cards
Its also heavily favored in the head-to-head matchup between the two
Yavimaya Elder (Ext, S, Block) A mainstay of The Rock (a black-green deck that thrives off of card-advantage creatures), the Elder potentially nets you a four for one advantage: it can block and kill a creature, then sacrifice to draw a card plus two lands
Mana Drain Mana Drain is a definite standout among the best blue cards MTG has ever released simply because its a counterspell that turns defense into an explosive mana advantage on the next turn