The abyssal serpent Messmer

Messmer is a Demigod who is encountered in the Shadow Keep. He is the source of Messmerfire and the Messmer's Flame incantations. Messmer is not an optional boss as he must be defeated in order to acquire Messmer's Kindling that would allow the burning of the Sealing Tree at the Church of the Bud. Background Messmer was born to Queen Marika the Eternal prior to the Second Liurnian War.[5] His birth was cursed by a dark entity, an evil serpent coiled within that threatened to subsume him.[7] Known to Messmer as the Abyssal Serpent,[8] this force was restrained only through Marika's intervention—she removed her son's right eye and replaced it with a seal of her Grace.[2] Ever since his accursed birth, Messmer was in constant company of the winged serpents, friends who suppressed the base serpent.[4] Much like his younger sister, Messmer bore a vision of fire.[7] He despised this flame, and time and time again hoped to rid himself of it, but found that it ever burned.[9] At some point, Messmer befriended Commander Gaius, an Albinauric who like him was cursed from birth. Gaius would go on to command Messmer's armies in the wars to come. They both acted as "older brothers" to General Radahn.[5] The Crusade

The Sacred Crusade Messmer conquered the hornsent Main article: Crusade Before the Shattering, Messmer was charged by his mother with carrying out a purge of the tower-dwelling hornsent of the Land of Shadow, who did not bear the light of grace.[10] At some point during his Crusade, Messmer was abandoned in the Land of Shadow, but continued to zealously enforce the purge even though Marika used him as a scapegoat and ceased all contact with him.[1] Messmer came to reside in a fort known as the Shadow Keep. Key in his army were the Black Knights, commanded by Black Knight Commander Andreas and his son and second-in-command Black Knight Captain Huw. Although they remained devoutly loyal to Messmer despite his abandonment by Marika, they ultimately rebelled upon learning of his serpentine nature. The pair were imprisoned in an underground tomb, and despite his betrayal, Messmer mourned the loss of Huw, whom he had considered a brother-in-arms.[11] [12] His Fire Knights rebelled against burning the Ancient Ruins of Rauh and the destruction of the specimens in the Specimen Storehouse.[13][14] Eventually, an intruder invaded Messmer's stronghold, the Shadow Keep, and was noticed by the demigod's serpents, who identified them as a Tarnished Champion and a pretender to the title of Elden Lord. Though surprised that a Tarnished had come to the Land of Shadow, Messmer nonetheless attacked them to continue enforcing the purge. However, the serpentine demigod struggled overcome the Tarnished. Unwilling to accept "a Lord devoid of light" and desperate to regain the upper hand, Messmer ripped out Marika's seal and unleashed the power of the Abyssal Serpent, allowing him to frequently transform into a massive serpent. Nonetheless, the Tarnished was able to land a fatal blow upon Messmer. Realizing that his mother had indeed forsaken him, Messmer used his dying breath to curse Marika.