My New Nemesis

The final Meta Achievement for War Within needs this achievement for it to be completed. I'm honestly not sure how that's going to happen for anyone who didn't manage to get it before the season ended. Will this mean that it'll be impossible to get the meta achievement..?

Edit: Listing this achievement as part of the meta "Glory of the Delver" is a bug on Blizzard's part. I just finished the last one I needed for it and it counted it anyway even though I didn't have "My New Nemesis."

Just beat The Underpin and got this achievement today as an ilvl 629 MM hunter. this fight is way easier than Zekvir imo, at least easier than Zekvir was at launch (Brann tanking aside). after defeating him i got the Golden-Gob Propulsion Rig (listed above as the reward from the achievement) as well as Brann's Spare hat from the quest. I also have the Explosive Victory toy, but the comments on that page seem to suggest it's bugged and being given to players without beating Underpin somehow? I never looted or learned it, it was just in my toy box when I checked after beating the boss, so not sure if i had it before and just never noticed, but the toy box says it comes from Underpin and I have it now, so I thought that would be worth mentioning.

as for the fight itself, there is only 1 phase (in tier 1 at least) and he has 185 million hp. his abilities are:

Crush - The Underpin will jump to a circle on the ground. don't stand in it. this hit me for about 6.7 million damage and if that doesn't kill you it stuns for 4 secs.

Flamethrower - big cone in front of The Underpin. it hits me for about 3.4 million damage and deals an additional 400k damage every 0.5s for 5s

Time Bomb Launcher - The Underpin shoots 5 bombs into the air which land on the ground and explode after 30 seconds. when they are about to explode you'll see a big orange circle. this explosion hits me for just over 9 million damage. The Underpin is pretty large, so you may have trouble clicking on these bombs. remember that you can use the Interact key (Default F) instead of clicking if you're struggling with this.

Call Cronies - summons 3 adds. these adds will shoot lines on the floor. the lines hit me for about 6.5 million damage. you can kick the Time Bombs into these guys before they explode to hit them for about 1/3rd of their hp. when these adds die they go up in flames. this is not just a visual effect, if you run into them you'll take about 700k damage every 0.5s. don't stand on them.

(Note: these adds are supposed to all spawn next to each other, but i noticed during my attempts they didn't always. sometimes 1 of them would spawn on the other side of the room making the rest of the fight much harder, because it made that last add harder to kill since the bombs would be on the opposite side of the room from where the extra add spawned, and you won't have enough bombs to kill the extra add until The Underpin shoots more. it also means if he summons adds where the extra add is, you'll get another extra add, since the first one is taking up the new one's spot. I haven't tested it, but my theory is that the adds spawn based on where the player is, and if you run too close to another spawn while the adds are still spawning it will split them up, so it may be best to not move too much while you wait for adds to spawn)

Divert Energy to Shields - The Underpin gains a shield for about 10% of his hp, and takes 100% increased damage for 20 seconds. while this shield is up he'll cast Recharge, which Heals him for 25% of his max hp at the end of the cast unless his Shield is broken first. when his shield is Broken he'll start leaking oil puddles on the ground. these puddles work like ice, you'll slide on it if you run on it and you take some damage. after he's done dropping oil puddles you should try to move him away from these puddles. if a bomb lands in a puddle it'll be much harder to aim that bomb at an add.

Good Luck

how to get that achievment in wow 11.2.5 for the future mount then, cause one of the things to get it is Glory of the delver......?
killed him just now and nothing.....