Katherine, Sword Dancer

Double Strike
Whenever Katherine, Sword Dancer attacks you
may have it lose double strike until end of turn,
if you do you may have it gain first strike until
end of turn. Then if it doesn't have double strike create a Create a 2/1 colorless Sword artifact
creature token with flying tapped and attacking,
if it has neither first strike nor double strike
create two of those tokens instead. Exile those
tokens at the end of combat.