Messmer is, without any exaggeration, one of the most brutal fights From Software put into Shadow of the Erdtree, and a good chunk of the community agrees he sits on the same shelf as bosses like Malenia in terms of raw difficulty. He's waiting at the top of the Specimen Storehouse, inside Shadow Keep, near the Dark Chamber Entrance Site of Grace, and by the time you reach him you'll already have climbed several floors of that library-like tower. If you've been stuck on him for a while, breathe, because that's normal — plenty of skilled players ate dirt there for hours. The first thing worth understanding is what he resists and what he doesn't. Messmer has high resistance to fire and to magic, which makes sense given he literally breathes flames and summons fire snakes throughout the whole fight. So forget pyromancer builds against him, that's swimming against the current. Where he actually struggles is frostbite and bleed. If you've got a weapon infused with frost, or an Ash of War that applies it, the fight gets noticeably more manageable, since the status still chunks a big slice of health at once and cuts down his aggression for a few seconds. Gear matters a lot here too. The Flamedrake Talisman, ideally the +3 version, helps a ton with holding off the fire damage, and it's found in the Fort of Reprimand, southeast of Shadow Keep — worth grabbing before you keep bashing your head against the boss. And don't skip the Scadutree Fragments available up to that point in the story, because they boost your damage and resistance in a way that changes the whole pace of the fight. People who go in without them basically take double damage. About the fight itself: in the first phase he's fast, strings his spear into long, unpredictable combos, and the most dangerous tell tends to be when he crosses his arm with fire before an attack, which usually precedes a straight-line lunge. Roll sideways, not backward, because rolling back just keeps you inside spear range longer. He also jumps and drops fireballs from the air — watch for a white smoke around him beforehand, that's the warning. The second phase is where things fall apart for a lot of people. He summons giant fire snakes, and here's a detail that changes everything: Messmer and the snakes share the same health bar, but they don't share a hurtbox. In practice that means if you can hit both at once — or land a status effect that affects both — you're basically doubling your damage per hit. Worth positioning your attacks around that instead of just focusing on him. If you summon Hornsent before the fight (which requires progressing his questline to a certain point), he helps quite a bit: he deals bleed damage, one of Messmer's actual weaknesses, and the neat part is his presence doesn't count as a summon for boss health scaling purposes, so you get help without inflating the boss's health the way a regular Spirit Ash summon would. Speaking of Spirit Ashes, if you're genuinely struggling, Mimic Tear or Black Knight Tiche are still solid picks, but make sure you've found the Reverend Spirit Ashes locations first, since that considerably strengthens those allies. For those who prefer a more patient approach, holding a shield and looking for parry openings instead of rolling everything is an option — his spear strikes do have parry windows, though they're tight and take practice. If you're playing ranged or with magic, accept it's going to be a war of attrition: stay constantly moving, dodge the jumps and explosions, and chip his health down bit by bit, knowing the damage will be lower because of his magic resistance. One thing that helps mentally with this boss is accepting you'll die several times before you memorize his patterns, especially the phase transition, which tends to catch people off guard. Once you finally take Messmer down, he drops the Remembrance of the Impaler, which you can trade with Enia at the Roundtable Hold for some genuinely strong rewards — and the rest of the game doesn't get any easier after him, so take the time to adjust your build before pushing forward.