When Rishkar, Peema Renegade enters the battlefield, put a +1/+1 counter on each of up to two target creatures.
Each creature you control with a counter on it has ": Add to your mana pool."
2/9/2017 Rishkar can be a target of its own triggered ability.
2/9/2017 You can’t target the same creature twice to have one recipient get two +1/+1 counters.
2/9/2017 Each creature you control has Rishkar’s mana ability as long as that creature has any kind of counter on it. The effect isn’t limited to those with +1/+1 counters.