Getting access to him is fairly easy. Gnomeregan is a low-level dungeon that’s been around in the game since its earliest days. It’s legendary for being too long and too hard for the point in the levelling curve it originally appeared, along with its general feel as a twisted, diseased and metallic vision of Gnome-hell. At level 110, it’s still going to take you a while to get to the end, but there’s no challenge about it. In the final boss’ room, there’s a tiny button hidden behind a pillar. Here’s a video of where to find it:
As shown, Endgineer Omegaplugg then shows up in the center of the room. He’s max level for a Legion boss, and spits out more damage with just his auto-attacks than everything short of raid bosses. The real problems, though, come with his special abilities. He’ll fire missiles and blasts of energy that do almost one-shotting damage to anyone who doesn’t dodge them in time, which they don’t give you much chance to do. The real problem, however, is the bombs.
As soon as the fight starts and throughout it, bombs will spawn from all the pillars in the room. If these reach players they detonate doing enough damage to kill basically anyone. There’s enough of them and they’ve got enough health that killing them individually just isn’t an option. They’re also the key to downing him, at least in some strategies. There’s no videos of it yet, but multiple Reddit users have confirmed that the bombs do damage to the boss if they explode on him. Kiting both the bombs and the boss around is how some have downed it, but those kills that have been detailed weren’t specific as to how it was done.
There is also now footage of the boss being killed by making the bombs despawn. Whether this is intended or not remains to be seen. There’ll be a full explanation before the day is done for sure, but if you’re feeling impatient, various streamers are now trying their hand on Twitch.