Wikia

The Slayer special property will increase the damage dealt to a specific creature type. In general this is more useful to mages, especially when it is a quest weapon with stats inferior to tinkered loot weapons. (By using the quest weapon, a melee/archer is usually giving up the chance to use armor rend or critical strike and so gains little, whereas the mage gets essentially a double vuln). If you are looking for all items that have a particular slayer property, see here.

Notes

Wands may have both the Maelstrom of Souls Gem and a slayer (Mukkir or Undead). Whichever is added last is the icon that will display on the wand and the wand will be attuned to the person that added the last item (even if the item was attuned to someone else who added the first item).

Slayer Types

Creature Type	Quest/Item
A'nekshay	A'nekshay Slayer Stone
Banderling	Tusked Axe of Ayan Baqur
Burun	Burun Slaying Weapons Regal Weapons
Elemental	Isparian Weapons
Food	Butter Knife of Slaying
Ghost	Spectral Weapons
Human (Bael'Zharon's Hate)	Assassin's Dagger Blighted Weapons Weeping Weapons Pillar of Fearlessness Royal Ladle Steel Butterfly Orb of the Ironsea Brador's Frozen Eye Spirit Shifting Staff Bearded Axe of Souia-Vey
Jester (Touched)	Ball of Fire
Lugian	Thunderhead
Monouga	Monouga Feeding Pit Quest
Mukkir	Mukkir Aspect of Grael Quest

Creature Type	Quest/Item
Niffis	Corsair's Arc
Olthoi	Aerbax's Prodigal Olthoi Gaerlan's Citadel Radiant Mana Infusion Quest Guardian of Pwyll
Shadow	Shadowfire Weapons Radiant Mana Infusion Quest Shadow Slayer (Live Event)
Skeleton	Radiant Mana Infusion Quest Spectral Skull Skullpuncher
Tumerok	Assault Weapons
Tusker	Tusker Paw Wand
Undead	Great BloodScorch Replica BloodScorch Search for Lunnum Eye of Muramm Staff of Fettered Souls
Viamontian Knight	Replica Sword of Bellenesse
Virindi	Singularity Weapons
Wisp	Black Thistle
Zefir	Zefir's Breath