Although four mana is quite a lot, Omnath, Locus of Creation stabilizes games incredibly well and does a bit of everything
Card Name Mana Cost Type Creature Elemental Rarity Common rules Text Whenever you cast a noncreature spell, if at least four mana was spent to cast it, put a +1/+1 counter on this creature
I dont know if youd ever want that many, but 25 might be a comfortable spot when the Damnation and Night of Souls Betrayal come in
Imagine you used Nihil Spellbomb and want to recur it but you'd also like to get out Seer's Sundial back)
Sephiroth, the Savior Four colors and 7 mana, but basically you win the game. Ideally youll get Atraxa, Grand Unifier earlier so you can build around it, as its among the best payoffs for UGx Towns
This will make you very scary at the table as a curve topper