Lovecraft superficially appears to be a tall, gaunt man with very emaciated features and dull, blank, dark gray eyes. He has dark navy, slightly wavy hair that reaches well past his waist, and is always seen pulled back so that it all falls behind him.
Clothing-wise, Lovecraft wears a white dress shirt and dark gray slacks, as well as a thin black belt around his waist. He wears a long tie, which is depicted as black in the anime, but patterned with a design of circles and diagonal lines in the manga. He wears a pair of dark gray loafers. Overall of this, Lovecraft wears a long, dark brown trench coat with three buckles towards the middle on each side. However, the most distinguishing feature of this coat is that it is in tatters, appearing nearly shredded at the bottom of the coat and at its cuffs.
When using his eldritch power, Lovecraft tends to contort his body parts, and his eyes become wider and almost blank. Moreover, he can sprout numerous tentacles dotted with suction cups and holes along their surface at random intervals, is undefined in length, and anywhere from his body. His true form appears as a humongous, tentacled entity with wings and a pair of glowing, seeming eyes. In the anime, Lovecraft's tentacles are portrayed as a shade of dull green.
Howard appears to be a fairly odd person, for example, as he and John Steinbeck were chasing after the Armed Detective Agency clerks, he was seen counting the wood grains before being told they weren't real. He also appears to be fairly nonchalant to battle, as he apparently fell asleep after being shot in the back by Doppo Kunikida.
After the Guild war, his oddness shows itself even more. As he states that since his contract with Francis Scott Key Fitzgerald is null, he'll be going to sleep, and thus he walks into the ocean.
Great Old One (旧支配者, Kyū Shihai-sha?) allows Lovecraft to transform either a part or his whole body into a monster with lots of tentacles. In this state, he is only vulnerable from the inside. Additionally, he is capable of regeneration. Notably, this skill is not an ability, as Osamu Dazai is unable to nullify it.
Lovecraft first appears with Steinbeck when he crashes his truck. He then, later on, appears with Steinbeck and the other Guild members during the conflict with the Armed Detective Agency and the Port Mafia.
Lovecraft then goes on to appear with Steinbeck after accepting the Mafia's proposal to capture the clerks of the Agency as bait, despite knowing that it was a trap. While chasing, Naomi and Haruno, Lovecraft, and Steinbeck are stopped by Tanizaki and Kunikida. They are later on seen fighting against Kunikida and Tanizaki but end up surrendering to the local police.
While in the city, he encounters Q on the streets by chance. He was then asked by Q to play with them. Thinking of a clown's balloon trick, he tries to give Q a dachshund in the form of his ability. Disgusted by what Lovecraft gave him, Q marks him using their ability. Lovecraft then transforms into a giant monster, scaring Q.
After the cursed rampage incident in Yokohama, Lovecraft, Steinbeck, and Guild operatives ambush Dazai who has come to rescue Q. However, Chūya Nakahara makes an unexpected appearance, hurling a boulder at Lovecraft and overwhelming the armed forces. The latter clashes with Chūya before transforming into his eldritch form, while Chūya activates his Corruption state. Dazai then sets off a bomb that he earlier embedded in Lovecraft's core, and Chūya finishes him off, ultimately resulting in the Guild members' defeat and Q's rescue.
When the other Guild members were discussing the fate of the Guild following the fall of Moby Dick, Lovecraft regenerates after his battle with Chūya. As he passes by his fellow members, Lovecraft mutters that the "contract" has finally been fulfilled before walking into the ocean to sleep.
- His ability, The Great Old Ones is a reference to Cthulhu's origins, a 'Great Old One' is a God of extra-dimensional origins.
- It is heavily implied by his dialogue about a "contract" with Francis Scott Key Fitzgerald that he actually is the "Great Old One" he transforms into, particularly due to him disappearing into the sea at the end of The Guild Arc.