This is the 'main' [Grendel] build that I've used for a couple of years now, adjusted to the Prime. Made very minor modifications.

You can avoid the second Umbral forma if you wish, and use an exilus forma instead, but I like having a full 16 points available to change between [Rush] and [Primed Sure Footed] if I want to.

[Firewalker] is a fun ability to use with Pulverize to leave some fairly powerful fire behind you as you roll around.