Game Mechanics: NPC attack immunity.

[Vohl]

I originally reported this as an issue with Intimidation skill in Runnyeye. I've since repeated the behavior in Lower Guk. It appears to be a synchronization issue of sorts between client and server. In either case, the problem occurs when a mob aggros and follows a long path to reach its target. In Lower Guk, I was not using Intimidation skill, but rather was pulling mobs over long distances. At times, the mob pathing would get screwed up and the mob would take several extra seconds to enter camp.

Frequently, when this pathing glitch happens, the mob is effectively invulnerable to melee attack by the puller. The mob can hit the puller just fine, but autoattack and secondary attacks all fail without any message. Curiously, other meleers as well as pets can hit the target just fine. I'm guessing that the issue in some way involves the server's consideration of whether or not a target is legal. On blue servers, I can target a PC and hit autoattack with similar behavior.

[Rallyd]

It's because the mob is under the world of sorts, you can see it but it took a bad path and that's what happens, if you clear your target and reacquire it sometimes it fixes it, known bug, very hard to fix, learn to pull with the mob on your ass and don't lose it.