Hij'qa was a Klingon warrior on the ship traveling to Gre'thor (or Klingon Hell), where dishonored souls were taken.
He approached B'Elanna Torres and held a branding iron to her cheek. However, it didn't brand the Klingon emblem upon her, as she was not yet meant to die. (VOY: "Barge of the Dead")
This Klingon was portrayed by Sherman Augustus.
According to the script, he was described as one of "four undead Klingon warriors [...] his eyes black and soulless."
The authors of the Star Trek Encyclopedia, 4th ed., vol. 1, p. 336 thought Hij'Qa "may (or may not) have been a hallucination."