Please be as specific as possible when letting us know what is missing or incorrect. For example, say "this game's trophy difficulty should be 8/10", with a link to a website corroborating this difficulty estimate (if possible), not "this game's trophy difficulty is wrong".
The Agent of Malekith collection contains two premium cosmetics for Kerillian: the Mask of the Shadow-Slayer hat and Naggarond Backstabber skin.
The cosmetics can be used on Kerillian's Shade career.
About the cosmetics:
Mask of the Shadow-Slayer - Hat Garb worn by the Shades of the Ashen Hills, whose footfalls leave no sound, and whose blades slice through armour as cleanly as skin.
Naggarond Backstabber - Skin Assassin's garb, worn by the particularly untrustworthy (distinctions matter in Naggaroth).