Howard Phillips Lovecraft is a former member of the North American organization known as the Guild. His background is deliberately shrouded in mystery, with no concrete information about his past or his reasons for joining the organization. He appears to be a tall, gaunt man of twenty-eight years with a gloomy and perpetually tired expression. His most distinguishing features are his long, dark navy hair, which reaches past his waist and is often pulled back, and his dull, blank dark grey eyes. He wears a white dress shirt, dark grey slacks, and a long patterned tie, all covered by a distinctive, tattered dark brown trench coat that appears almost shredded at the bottom and cuffs.

Lovecraft’s personality is as strange as his appearance. He is profoundly lethargic and seems to hate exerting effort, often telling his partner to finish jobs quickly because he wants to go home. He is extremely nonchalant, ignoring serious situations such as a vehicle crash or even falling asleep shortly after being shot in the back during a battle. His behavior is odd and detached from normal human concerns; on one occasion, he paused while chasing a target to count wood grains, only to gasp in shock upon being told they were merely laminate. He dislikes being the center of attention, as it makes him itch, and he is seemingly always anxious.

His motivations are remarkably simple and contractual. Lovecraft does not appear to care about the Guild's grand ambitions or the conflict over Yokohama. His sole stated reason for acting is a contract or promise he made with the Guild's leader, Francis Scott Key Fitzgerald, whom he addresses with a peculiar familiarity. Once this contract is fulfilled, he has no further interests. His primary desire, expressed multiple times, is simply to sleep, which he does for years at a time during his downtime.

Within the story’s narrative, Lovecraft serves as a formidable enforcer for the Guild, typically partnered with his colleague John Steinbeck. Their partnership is one of the few key relationships he has, though it is based more on utility than friendship. His role becomes critical when he single-handedly captures Kyūsaku Yumeno (known as Q) of the Port Mafia, whose powerful ability is unharmed by Lovecraft's unique constitution and is then used as part of a city-wide ruin plan. This act forces a temporary alliance between his enemies, Osamu Dazai of the Armed Detective Agency and Chūya Nakahara of the Port Mafia.

In terms of personal development, Lovecraft remains largely static, a force of nature rather than a character who changes. His mysterious nature is reinforced throughout his arc, culminating in his surprising survival and departure. After the Guild is defeated, he regenerates from a devastating internal explosion and being seemingly destroyed by Chūya’s most powerful attack. His parting words are that his contract has finally been fulfilled, and when asked about his future plans, he simply responds with "Sleep" before walking into the ocean and disappearing, his ultimate fate unknown.

Lovecraft's most notable feature is his ability, which he calls "The Great Old One". This power allows him to transform his limbs or his entire body into a massive, winged, tentacled monster. In this state, he possesses immense superhuman strength, speed, and durability, easily crushing opponents and surviving explosions. His most terrifying trait is his incredible regenerative healing factor, which allows him to recover almost instantly from lost limbs and even reconstitute his body after being blown apart. A crucial detail that underlines his inhuman nature is that this power is not considered an ability within the world's rules, as Osamu Dazai's nullification power has no effect on him. Furthermore, his mind is so alien that he is completely immune to all forms of mental interference. His only known vulnerability is from inside his transformed body, as demonstrated when Dazai detonated a bomb within him to allow Chūya to land a decisive blow.