Only creatures you control when Selfless Cathar's ability resolves will be affected. Creatures that enter or that you gain control of later in the turn will not.
22-09-2011
wotc
You can activate Selfless Cathar's ability even if you control no other creatures.
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.