I was previously only aware of its ability to freeze on crit (which is pretty cool), and never knew about the singularity/cryo nova (with similar 100% proc chance to freeze). I mean it describes this in the Wiki, but I play a loose elemental allegiance, so Wilhelm was the only character using this weapon (and I only melee with Power Fist, which doesn’t proc the singularity cryo nova). Let me spell this out a bit for the uninititated:
*If you shoot something and score a critical hit with it, they will freeze (if it doesn’t outright kill them). For the record, I have shot enemies, seen the “critical” pop up and had them not freeze, but it’s rare.
*If you melee something in the critical location, they will freeze.
*If you melee a frozen enemy (crit not required), you will generate a singularity effect centered on you. This will be followed by a cryo nova that freezes anyone caught in it. It doesn’t seem to matter how the target was frozen either, but sometimes if they die when you hit them, it won’t proc (I think it comes down to a tie or close race between cryo DoT killing them vs the timing of your melee strike).
*If you enter a vehicle with the Excalibastard equipped the freeze-on-crit effect transfers to the turret. You need to select weaponry capable of critting, and then you need to crit something, but it does make the Shuggurath easy to deal with (for example).
Seriously, this weapon is awesome. Freeze the biggest guy in a mob, melee him a few times to proc singularities that draw everyone else in, who then freeze with the cryo nova, and then repeat with the little graveyard of frozen dudes. The cryo nova even takes a moment to fire, so if enemies are behind cover, you have a moment to run to them to catch them in the freeze.