Drain Life with the Stagger node is capable of permanently stunning everything that isn’t stun-immune. Based on some answers on Discord, I believe this is a bug and it is supposed to only be able to apply once per mob, however it can currently be applied repeatedly.
The long description of what exactly happens:
- Drain Life has a passive called Stagger, which applies a guaranteed 2 second stun after channeling on an enemy for 3 seconds continuously.
- The following node, Stupefy, increases that stun to 4 seconds.
- Channel Drain Life until you see the Contempt buff pop up on your bar (lets you know exactly when Stagger has triggered).
- Stop channeling and go to step 3 until the monster is dead.
Enemies seem to be capable of activating instant cast abilities every time you reapply the stun, which makes it hard to pin down some bosses like Rahyeh or Julra, but some bosses are made completely trivial with this, like Heorot who is unable to even activate his add phases.