[Legacy] Pestilence Combo

Practically every card combos with Pestilence. Use Diabolic tutor to find it when you need it. The Crypt Rats function like a one-time Pestilence bomb; the nice part is they can go as high on X as they need as long as you blow it all in one big wad.

The Darksteel artifacts won't die to Pestilence. Soul Link them, a Wall of Hope, or best - the enemies' trump beast he just played. Use Pestilence on the Wall for X = 2 to gain life each time, or if it's on the enemy for X = Toughness - 1. Soul Link also completely shuts down their ability to use that creature offensively as long as your life stays over its Power.

The Circle and Runes can directly prevent you from taking damage from Pestilence, the only downside is you have to pay per activation of Pestilence. They DO work much better on the Crypt Rats bomb at 1 mana, however.

If you draw a Tainted Sigil, use it when you pull off a gigantic Pestilence attack to regain your lost life and the opponent's for the turn. Particularly effective in multiplayer as it specifies all players.

If you already have a Pestilence on the board and draw the Rats, wait till you have a second creature in hand, or an indestructible on the board. Use Tainted Sigil, Soul Link, or Wall of Hope and pay as much for the Pestilence effect on the Rats as possible - you might lose your Wall or your one-time Sigil but you will have dealt a huge amount of damage. Save just enough to cast a creature by end of turn if you need to keep Pestilence on the board.

The only thing that really poses a challenge for this deck is creatures with Protection from Black - but the artifacts and Walls can block them effectively.