Addressed as a letter to a "monster," KGBlack's poem reads like a portrait of something that has settled into the speaker's life and won't go away. The monster could be a person, a habit, or a state of mind such as depression or an unhealthy relationship. The poem never says, and that openness is part of its pull.
The speaker has lost track of time ("years or minutes"), and the black, dripping imagery suggests something dark seeping into their thoughts. The monster promises closeness, "together forever," but the speaker feels time running out. The description of strong fists, blue eyes and a small body is odd and unsettling, as if the threat is less obvious than it seems.
The mood is tired, uneasy and torn. The repeated "Dear monster" sounds both affectionate and accusing. The last line, "what would I do without you," is the most telling: the speaker fears the monster, yet has come to depend on it.