For reasons that will become apparent on launch, it drops a leaf-bladed sword. The creature is best fought with Magic, so its other drops can include runes to help with the cost. However, it's in the forthcoming new dungeon which is assignment-only, so players won't be able to grind there incessantly to flood the market with runes.
The graphic's adapted from the Sea Troll Queen. She looks pretty cool, but you only ever get to see her once during a quest (and she wasn't suitable for the NMZ cavern either). Also, since she's clearly not genetically identical to the sea trolls who server her, this may be an opportunity to extend her species a bit.
