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.
01-01-2011
wotc
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.
01-01-2011
wotc
The mana can’t be spent to activate activated abilities of Myr sources that aren’t on the battlefield.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.