This boss is found in the zone "Sanctum of Flame," and is arguably the easiest of the gland bosses and is therefore recommended to fight first.
Considering most of his attacks are pretty basic, slow, and easily telegraphed "fat boss" attacks, there isn't too much to say in terms of fighting him, but there are still some tips worthy of mentioning. Don't forget to talk to Sester Genessa on the left before drinking the magical teleporting poison juice to start the fight.
Phase 1
+As stated, most attacks are slow and easy to predict but they all consist of some variety of him swinging his mace. You can harden through one of his hits, even the non-parry kind, but simply rolling works as well. Wait for him to finish his combos and you will have time to get several attacks in as his recovery time is very long.
+If his mace glows a brighter orange, do not get hit by it! This will apply a burn effect on you which is really the main threat of this boss. This burn will do a large amount of tick damage to you, however if you remember your basic fire training and stop, drop, and roll, it won't be able to damage you so long as you keep rolling for the duration. This will eat away at your stamina though and therefore shells with more stamina (like Tiel) are better for this fight. That or just...don't get hit? Hardening can also negate the tick damage for some time, as well as prevent the burn from applying in the first place.
+Due to eating too many spicy wings, Imrot will sometimes blow fire back and forth. If you are close it is recommended to harden through the full attack. It will apply the burn if it contacts you non-hardened.
+His most exploitable attack happens when you have distance with him. He will charge at you and swing his mace diagonally twice. You can simply step back as he does this and then go in for free hits right after. This attack always glows so don't get hit by it. If you are patient you could just keep baiting this attack out of him.
Phase 2
So there is almost no real difference with phase two other than you can now look him in the eyes while you kill him due to him loosing his helmet. He will get all his health back, and more of it, but everything from phase one is pretty much applied here minus a little bit of different ways to swing the mace. That and now he can kick you.
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Good luck on cooling off the hot one!