Elemental Resonance

2006-05-01 If the enchanted permanent's mana cost is {2}{W}{U}, this Aura's controller adds {C}{C}{W}{U} to their mana pool. If its mana cost is {X}{G}, this Aura's controller adds {G} to their mana pool. If its mana cost is {W/U}{W/U}, this Aura's controller chooses whether to add {W}{W}, {W}{U}, or {U}{U} to their mana pool. The choice may be different each time the ability resolves.
2006-05-01 Only the first main phase in a turn is the "precombat main phase," even if additional main phases are generated by some effect.
2006-05-01 This ability isn't a mana ability. It uses the stack.
2009-10-01 You get the mana whether you want it or not. If you don't spend it, it will disappear at the end of the current step (or phase).

mtg.wtf