Lovecraft superficially appears to be a tall, gaunt man with very emaciated features and dull, blank, dark gray eyes. He has dark, 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 "Ability," Lovecraft sprouts numerous tentacles dotted with suction cups and holes along their surface at random intervals, and is undefined in length. In the anime, these 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 Companies Clerk's 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 Kunikida.
After the Guild war, his oddness shows itself even more. As he states that since his Contract with Fitzgerald is null that he'll be going to sleep, and thus he walks into the ocean.
Great Old One (旧支配者, Kyū Shihai-sha?) is an ability that allows Lovecraft to transform either a part or his whole body into a monster with lots of tentacles. And in this state, he is only vulnerable from the inside. In addition, even after being destroyed from the inside by Chūya and Dazai, he eventually regenerates.
It is later known that Great Old One is not an ability as 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. 
Lovecraft, together with Steinbeck, makes an appearance again where they both ambush Dazai who came to rescue Q. However, Chūya makes an unexpected appearance, resulting in their defeat and Q's rescue.
- His ability, The Great Old Ones is a reference to Cthulhu's origins, a 'Great Old One' is a God of extra-dimensional origins.
- The Great Old Ones is not an ability.
- 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.