You inject or expose a target to a hemotoxic agent that destroys blood cells and weakens the body from within. Victims suffer internal bleeding and take increased bleeding damage when struck.
At the end of the round, target suffers 1d4 internal damage + 1d4 extra damage per hit taken.
This damage is accumulative, so if target takes 2 hits in the first round, the damage will be 3d4 in that round. If target then takes 2 extra hits the second round, then the damage will be 5d4 at the end of the second round.
For each +20 success rate, increase the die by 1 size. 1d4 -> 1d6 -> 1d8 -> 1d10 etc.