He is called the "Doomsman of the Valar," and he "pronounces his dooms and his judgments only at the bidding of Manwe" (19).
Closely tied in with the notion of judgment as one's fate or doom is the personification thereof, as is transparent, for example, in Mandos, "the Doomsman of the Valar" (19).
In The Silmarillion, we know that the Doomsman of the Valar, Mandos, pronounces his dooms "only at the bidding of Manwe" (19).