Avery attended Hogwarts at the same time as Tom Riddle, Jr., and was sorted into Slytherin house. He became a member of Riddle's gang and was a favorite student of Horace Slughorn. Avery was present at the same Slug Club meeting in 1944 or 1945 as Tom Riddle and was reprimanded by the Potions Master for failing to hand in a particular essay. After Hogwarts, Avery became one of the first Death Eaters.
Avery likely fought in many battles during the First Wizarding War. It's unknown if he was killed, imprisoned, or escaped capture after his master's downfall. If he was still alive he may have also fought in many battles during the Second Wizarding War, including the Battle of Hogwarts, however he likely would've been killed or sent to Azkaban after the battle assuming he wasn't already dead.
- Avery, Jr. (possibly)