Scryer's Purgatus Psyker
 Psyker Build - Warhammer 40k: Darktide 

This build probably isn't the best Purgatus build, but it is unique and works surprisingly well (as long as you are careful not to explode - don't charge the flame over (or close to for safety) 100% and release). This build will also easily generate the most crits in the game - Purgatus is already a crit machine, and with the extra +20% (and optionally +5% from the Prescience aura if you want to switch), you'll easily be tripling everyone else's total crits, even compared to Blazing Piety riposte scourge knife zealots.

The idea behind this build, is to be spamming Scryer's gaze as much as possible with the Purgatus staff. A max purgatus staff barely generates any peril compared to every other staff, and combined with the two -5% peril gen nodes and Inner Tranquility, you won't even notice peril generating. The purgatus staff already gets crits galore, so now with a 50% crit chance you can get 4000+ crits a regular pub game with 500k enemy damage. Warp Siphon is used because Inner Tranquility lets you generate even less peril. It will also ensure you have close to 100% uptime on Scryer's.

You can take Disrupt Destiny, I just feel its not as useful for the Purgatus staff since weakspot damage is not triggered by it, wasting part of Disrupt Destiny's buff and making the True Aim talent node useless. The big reason to pick this is definitely for Purloin Providence potentially extending the duration.

Quietude is taken over Perilous Combustion to help extend Scryer's longer, but feel free to switch. Also make sure you are quelling during Scryer's - at least until you get your Warp Siphon stacks back to prime the next Gaze - you can extend the duration super long.