This addon displays all the onhit damage a player/npc has. So if you are about to frenzy as a cursed with two weaspons, which means 4 x 2 = 8 hits, and the npc does 100 cold damage, you'll gain for yourself 800 hp damage! This addon adds the 100 cold type info to the tooltip for any player/noc, so you can decide what to do BEFORE hitting it.

This info is available under Inspect Creature | Defence | Damage when hit column.