The Yeti is featured in the Myths of the White Lands quest, released with the 2008 Christmas event. Players have to complete a series of puzzles to get into the Yeti's final room. However, to obtain the stones ('riches' that Explorer Jack seek), the yeti has to be subdued.
To do this, players have to travel back a couple of rooms and access the upper level. Once at the upper level, players need to return to the yeti's room, and blow a pipe. This knocks the yeti unconscious, and once the yeti is asleep, players will be able to aqcuire the stones for Explorer Jack. If a player does not do this, the Yeti shouts and shakes the cave, forcing the player back out its lair.
One interesting note is that during the quest, it is an NPC, and has yellow text when examined. After the quest is completed, the text becomes a piece of interactive scenery, its examine text becoming blue.
Yeti dung has a horrible stench, and acquired during the quest in the form of stones and enchanted stones.