Wildcall
{X}{G}{G}
Sorcery
Manifest the top card of your library, then put X +1/+1 counters on it. (To manifest a card, put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)
Zaxara, the Exemplary
{1}{B}{G}{U}
Legendary Creature -- Nightmare Hydra
2/3
Deathtouch
{T}: Add two mana of any one color.
Whenever you cast a spell with {X} in its mana cost, create a 0/0 green Hydra creature token, then put X +1/+1 counters on it.