Jindu, Mass of Might

Each player may activate Jindu's abilities only during his or her upkeep.
You may cast creature spells with converted mana cost equal to the number of +1/+1 counters on Jindu without paying their mana cost.
{g/u}{g/u}: Put a +1/+1 counter on Jindu.
{b/r}{b/r}: Put a -1/-1 counter on Jindu.