Shalazam

It is a "dusk" spawn Kill ph at after 1400 and before 1600 game time to get the spawn(50ish% chance). Can also spawn at the same hut in the other quadrant. /loc of other spawn location is -100, -1821. PH there is the same Voidwalker that paths from the hut to the circle. Credit to Korruptd, Naz, Fogerty, Calyadwin and others who spent the time to figure it out.

Also sold by Fiona Draster (Tailor) in the Village of Availia

Pretty sure the flavor text about causing them to miss is just justifying the Parry mod

It's likely something else breaking mez for your group. This sword does not have a proc and hasn't had a proc since it started dropping. I've beaten on the availia training dummies with this for upwards of 10 straight minutes with nothing but auto attacks and there are no procs. Likely culprits - someone in your group is using the wavecrasher sword from BRK, the tank has a damage shield buff like from a summoner, or something else has some minor aoe. Check your combat logs when it happens to be certain.

drops hangore or EP wolves i'm told