Doomsday Confluence lets you choose between more daleks, making everybody discard, and/or sacrificing stuff
Plus, grabbing Energy from the discard pile is surprisingly easy
Lastly, the back face doesn't have a mana cost, but its mana value is based on the mana cost of the front face
But instead of interacting on the stack, youre interacting with your opponents using a stack (of sharp implements)
Youll generally be happy to use this for one of the two abilities, but being able to use both makes it an incredibly efficient and flexible spell that deserves a slot in many green decks
Much of its power comes from effect manipulation rather than brute force, so decks relying on removal or disruption often struggle