Sligoil was designed to belong to a company that does not exist. Ariel Martín Pérez drew it as the interface monospace for the video game Unknown Number, where Sligoil is the name of an evil fictional oil company, and the typeface had to read like the cold, functional lettering such a corporation might stamp across its screens and paperwork. Built for an imaginary world, it turned out to have real character. Its letterforms gather influences from an unexpectedly specific set of sources, all drawn from the culture of the British Isles.

There is the lineage of Matthew Carter's work, the great type designer, and the hand-painted signage of Irish whiskey distilleries, that particular blend of confidence and age. Layered onto that is something more technical: the keycaps of MIT's vintage Space Cadet keyboard, the legendary early machine whose keys bristled with symbols. The result feels both regional and mechanical, a monospace with a sense of place. Being a fixed-width face, every character occupies the same slot, which is what makes it read as an interface font, code-like and orderly, exactly the texture a menacing corporation's terminals would have.

Sligoil has kept growing beyond the game that spawned it. A 2025 update added Vietnamese support, extending its reach to another writing community, and introduced two new weights, giving designers more range than the original single cut allowed. It is released through Velvetyne, the open foundry, under the Open Font License, so a monospace invented for a villain in a video game is now free for anyone to use, whether they are building an interface, setting code, or simply drawn to letters that carry whiskey signs and old keyboards in their bones.