Tangleroot

Whenever a player casts a creature spell, that player adds {G}.

Darting Merfolk

{U}: Return Darting Merfolk to its owner's hand.

Ramos, Dragon Engine

Flying
Whenever you cast a spell, put a +1/+1 counter on Ramos for each of that spell's colors.
Remove five +1/+1 counters from Ramos: Add {W}{W}{U}{U}{B}{B}{R}{R}{G}{G}. Activate only once each turn.

Hardened Scales

If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on it instead.

False Dawn

Until end of turn, spells and abilities you control that would add colored mana instead add that much white mana. Until end of turn, you may spend white mana as though it were mana of any color.
Draw a card.