It has a chance on kill to raise a skeleton minion. (My guess is around 10% chance.) The skeletons last for a few minutes. Upon raising the 5th, the skeleton explode and the sword transforms to Ashbringer for 30 seconds, which deals 5000–6000% weapon damage as Holy on attack.
Therefore, the uptime of Ashbringer depends on killing speed. It can be a decent weapon in dense rifts / greater rifts.
I have done some testing with an ancient CAB on my wiz and it wasn't that great. I did see some damage spikes when the proc was on but not sure if it was enough damage and if it's worth it to give up on something like 50% elite damage r 20% elemental damage for that proc...
I tried to aim it so i kill a lot of white mobs and when it procs i move on to an elite pack but the problem is that the duration of the proc is also very short. Maybe in a perfect rift it could work well but i'm not sure how to utilize it properly to be honest.
Also, i have no idea how the skeletons work exactly, you can't even see them while in the middle of a fight in a GR... They need to add buff icons for this shit (fix the limited buff icons issue first obviously).
When the top left skellies icon counts to four, then disappears, you know it has just transformed.
Yeah noticed that while testing again yesterday. For some reason the damage from the CA does not show up as damage numbers / crits... Not sure why.. I tried a few GR 50-54 solo on wiz tal build and it felt like running with a random 2 handed weapon. I'm sure there is a way to utilize this weapon properly but it's just not working for me. And as others said, during the rift it ususally procs when everything is already dead, and on RG's it doesn't proc at all (depending on the RG)... I don't know, i need to do some testing on Ghom i guess - Let him spawn those slimes, untill it procs then see.