A seer or prophet. The Lake of Hali appears to be named after him. Lovecraft mentions the lake. Bierce originated the name in "The Inhabitant of Carocosa" and "The Death of Halpin Fraser."  Robert W. Chambers took the character for his "King in Yellow."  It is most likely that Bierce took the name from the expression "Ayn Hali," which means "the Eyes of Ali."  This can be found in the author's notes of "Lalla Rookh" which both Bierce was familiar with. August Derleth and Mark Schorer expanded Hali's fame to a godlike level, in "The Lair of the Star-Spawn," claiming that Hali was banished in the Hyades when Hastur was also banished and Cthulhu was exiled in R'lyeh.

[The Whisperer in Darkness - H.P.L.]