"They come because I call. They stay because I listen."

Beastcaller Savant

Haste
{T}: Add one mana of any color. Spend this mana only to cast a creature spell.

Battle for Zendikar Promos

Battle for Zendikar

Haste{T}: Add one mana of any color to your mana pool. Spend this mana only to cast a creature spell.

Mana produced by Beastcaller Savant can be spent on any part of a creature spell’s total cost, including additional costs (such as kicker costs) and alternative costs (such as dash costs). It can’t be spent to pay the costs of abilities of creatures you control.

Mana produced by Beastcaller Savant can’t be used to activate an ability or cast an instant or sorcery spell that creates creature tokens.