Black Fester

This black paste is often applied on orc weapons before going on raids to stymie an enemy’s healing magic.

Source Advanced Race Guide

Like a poison, black fester stays on a weapon until the first time it strikes an opponent. It remains in the target’s body for 1 hour. A creature exposed to black fester resists magical healing; a creature trying to magically heal the target must make a DC 10 caster level check to restore any hit points to the target.