Scarlet Onslaught Trunk Key

This key opens Scarlet Onslaught Trunks found at Onslaught Harbor.

Source
This key drops in Icecrown from:
 * Onslaught Gryphon Rider
 * Onslaught Harbor Guard
 * Onslaught Raven Bishop
 * Onslaught Paladin
 * Captain Welsington
 * Captain Hartford