I've wasted 80+ exp so you guy's didn't have to, you cannot recoil this boss. And he despawns in a certain time. The goal is to poison him within 1 minute; you need to hit him once and there's a 2/3 chance he'll get poisoned.
HOWEVER, in 80+ exp gained, I've never hit a 1. ONLY 0's, yes hitting 0 and getting exp. I've reported the situation to Jagex in attempts to fix this, but the only way I can see this boss dying at the moment would be to 10+ people venging you. I had 4 vengers and got it to half life before it despawned.