Leading the 5th Fellowship, he commanded the Athanaean Cult, the telepathy specialists of the Legion. A native of Prospero, Uthizzar took command of the 5th Fellowship after the previous captain Apophis was killed in battle against Orks. Uthizzar later briefly battled the Space Wolves during the Ark Reach Secundus incident where many of his Athanaeans were killed by the psychic backlash caused by Leman Russ.
Later after his failed attempt to warn the Emperor, Magnus fell into a depression. He was confronted by Uthizzar who was accidentally exposed to the Primarch's psychic power. In an instant, Uthizzar saw much of Magnus' past including his secret dealings with Tzeentch in an attempt to rid the Thousand Sons of their Flesh Change mutation. Horrified by what he had seen, Baleq attempted to leave to inform the rest of his Legion but was killed by a psychic blast by Magnus.
Not to be confused with Uzthizarr, a character who only differs from Baleq Uthizzar in the slightly different spelling of their name, and that Uzthizarr survives the Battle of Prospero and becomes a Daemon Prince