Goblin Electromancers effect reduces the casting cost in terms of total cost
The Ravenous Rotbelly can sacrifice up to three Zombies as soon as it is put into play, for which each opponent has to sacrifice the same number of creatures since there is no actual Boardwhipe in the deck, this can reset the game
The first mode can kill a smaller creature, or pump up a sufficiently large attacker, which you could even use on an opponents creature to ensure both attacker and blocker die in the exchange
This is a one-mana, repeating card draw effect in White
SO, WHICH ENERGY PRECON IS BEST
Whenever you cast an instant or sorcery spell, if it targets one or more other permanents you control, create a token that's a copy of one of those permanents