- The Decepticon High Council is a body in the Marvel UK portion of the Generation One continuity family.
As the Council were only seen once and then never again after appointing Thunderwing as leader, they could have been a temporary body to deal with the then-current leadership crisis. In the year they were seen (1989), Ratbat, the Triumverate and the Megatron clone all died in a relatively short space of time; Scorponok was on Earth and showing no real sign of focusing on Cybertron; and Shockwave and Megatron were deliberately pretending to be dead. Appointing a new leader would have been a matter of some urgency.
(If not a temporary body, we would have to assume Megatron would form or allow a body that could appoint someone else as leader...)
Marvel Comics continuity
Thunderwing made a bid for Decepticon commander, and was set a test by the High Council.He failed and a team was sent to retrieve him, which he commandeered to attack the Ark. The Council was impressed by this ballsy move and appointed him commander.