What are the official rulings for Myr Reservoir?
user
0. A card, spell, or permanent is a Myr only if it has the subtype Myr, regardless of its name. For example, Myr Reservoir itself is not a Myr.
1. The mana can’t be spent to activate activated abilities of Myr sources that aren’t on the battlefield.
2. You can use the mana produced by Myr Reservoir’s first ability to pay an alternative cost or additional cost incurred while casting a Myr spell. It’s not limited to just that spell’s mana cost.
assistant