Grim Dawn Development Update

In his fourth "Grim Misadventures" post to the official Grim Dawn forums, Crate Entertainment's "Zantai" shares the stats for a weapon called the Herald of the Apocalypse, a screenshot of the weapon's primary ability, a hint at a new mastery (called Nightblade), and more. Great stuff:
Some questions were raised earlier regarding how our item skills will work. To get your mental gears rolling, here are some possibilities:
- Activated on hit by enemy (any / melee / projectile)
- Activated on your attack
- Activated on your low health
- Granted (you can add it to your skill bar)

The chance of the activated skills triggering is not modified by attack speed (yours or your enemy's), so faster attacks will benefit more from item procs. Slower weapons have their own benefits though.

Two weeks, one item done! Whew, what a workload. I may need a holiday. What! Considering the possibility that I may have actually worked on something else, something even more awesome? How much awesome can we handle in an update?!

Well, alright. Here is a little hint. It starts with (Nightbl) and ends with (ade Mastery).