Waste Not Waste Not is a pillar of any strategy that cares about your opponents discarding cards or denying them resources
What it lacks in colored mana, it makes up for with Library, Strip Mine, and Regrowth to potentially bring back one of the former
For , this Instant deals damage equal to two plus the number of Lessons in your graveyard to a Creature and exiles that Creature when it dies
Unholy Annex // Ritual Chamber Phyrexian Arena, but with a significant upside (you don't even need to lose life!)
Even without getting to deal 10,000 damage, taking one more removal spell from an opponent's hand is still a useful benefit
Pact of the Serpent can either be used to draw you a ton of cards or kill an opponent, depending on the number of Squirrels you have