You’ve learn to chain different tier 4 weapon skills with an ally.
Prerequisite(s): Any tier 4 weapon skill feats, BAB +11.
BENEFIT
At the end of a round of combat, if you or an ally with this teamwork feat starts a chain by using 2 or more tier 4 weapon skill feats will activate this feat automatically, causing the target creature of the weapon skills to take 20 points of non-elemental damage per weapon skill used during the round, no save.