Your orc heritage allows you to fight on.
Prerequisites
Con 13, half-orc, orc ferocity racial trait.
Benefit
You gain the ferocity universal monster ability, allowing you to continue fighting at negative hit points. When using this ability, you gain a +2 bonus on Intimidate checks.
Normal
A half-orc with the orc ferocity racial trait can fight for 1 more round after he is brought below 0 hit points.