Parapet of Slaughter

Fortify {1}{w} ({1}{w}: Attach to target land you control. Fortify only as a sorcery. This card enters the battlefield unattached and stays on the battlefield if the land leaves.)
Fortified land has "Whenever mana produced by this land is spent on a creature spell, that creature gains Bloodthirst 1. (If an opponent was dealt damage this turn, this permanent enters the battlefield with 1 +1/+1 counter on it.)