mtg search library for a card c!u o:"search your for" · Scryfall Magic: The Gathering Whenever your commander enters or attacks Rules Text: Search your library

This is valid, but its also valid to wait to pay for the spell until the final step of casting a spell: 605.3a A player may activate an activated mana ability whenever they have priority, whenever they are casting a spell or activating an ability that requires a mana payment, or whenever a rule or effect asks for a mana payment, even if its in the middle of casting or resolving a spell or activating or resolving an ability

Plus extra cards

Squirrel Wrangler Squirrel lovers will go nuts for this one

(6/13/2017) If two or more effects require a creature to attack different players or planeswalkers, such as that of this scheme and that of Gideon Jura's first ability, that creature's controller chooses one to fulfill