At last, the much-anticipated level 52 opened up for me like a flower, permitting me to partake of its sweet nectar: a Demonslayer sword bearing a Demonslaying enchant. This was the first item Gweryc had used that I actually considered a twink. Characteristically, I'd found the sword itself at a bargain price using Auctioneer. However, the enchant was donated by my main, who had rather fortuitously bought the Enchant Weapon - Demonslaying formula at nearly the same time I'd found the sword.
The sword itself, I'm sorry to say, was a tremendous disappointment. Although the sword is a natural host for the enchant, the +99 AP on the Demonslayer just doesn't make up for the loss of the stats on my Ice Barbed Spear. Let us speak no more of that sword, forever.
So what about the enchant itself? Demonslaying has a chance on hit of afflicting a demon with Smite Demon, dealing 75-125 Holy damage and a 5 second stun. Reports on the proc rate are mixed. Some claim it procs so infrequently it's not worth it, while still others claim several times per fight. The most reliable reports claim about 2 ppm.
Demonslaying is definitely better than a sharp stick in the eye, but it too fell short of my expectations. I confess that I didn't observe the exact performance of the enchant with my usual statistical rigor, so I can only offer anecdotal evidence. When it procs, it's a Very Good Thing. The Holy damage is nice, but the real win is the stun. I was generally able to take off half the demon's life before he recovered from that stun. However, the stun didn't proc nearly enough for me to feel as overpowered as I'd hoped. It certainly wasn't bad, but it was hardly imbalanced, either.
I like predictability. When I pay for an enchant, I want to have confidence in what it can do for me. Yes, I did better with this enchant grinding on the demons of Felwood than I would have without it, and I did appear able to cause it to proc off Wing Clips as I'd hoped. However, the enchant didn't proc on the majority of fights. Like critical hits, the effect it yields is a pleasant bonus, but it's not something you want your life to depend on. (And unlike critical hits, there's no gear I can obtain to increase the proc rate.) Down the road, this has really discouraged me from taking the proc-based Mongoose enchant over the reliable Savagery or Major Agility.