Varterral

Varterral or striders are huge spider-like creatures that stand on four massive legs and move with surprising speed. They spit corrosive poison and are able to leap after prey.

Background
These creatures are deadly guardians, often associated with the lost, ancient elven culture of Arlathan and the times before that the elves have lost to history. It is said that these strange creatures were created by the gods from rock and tree and wind and rain to protect the elven people.

Though unconfirmed, some hints are dropped during Witch Hunt that might point towards the Varterral’s less-mythical origins: it is classified as a dragon. Its description states, in these words, ‘Dragon, Level 38 Boss’, when you mouse-over its red dot on the minimap with a character with Master Survival. The Warden will also exclaim "Watch out for the dragon!" Now, this could be nothing more than a meaningless class name, but if the varterral is a dragon that would explain why it was in the Dragonbone Wastes and so many cultists were around.

Witch Hunt
A varterral appears as the final boss of Witch Hunt, the final DLC for Dragon Age: Origins.

Dragon Age II
This is the first new creature for Dragon Age II to be described on BioWare's site. One appears in the Destiny trailer. In BioWare site and concept art, is called strider but from the achievements of Dragon Age II and so probably in-game, they will called varterral.