Alley Psychopath

Deathtouch
When Alley Psychopath enters the battlefield, if its stalk cost was paid, it gains first strike until end of turn.
Stalk {3}{b}{b} (At the end of each block step, if there is an unblocked creature attacking you,
you may cast this card for its stalk cost. If you
do, choose an unblocked creature attacking you. This creature blocks that creature.)