Few people leave the ranks of Cobra and survive. Mercer, alias Felix P. Stratton, is one of them. Smart, strong, and just plain mean, Mercer's one asset Cobra regrets losing.
Devil's Due G.I. Joe vs. the Transformers comics continuity
As a member of Cobra, Mercer helped move the stasis-locked Transformers out of the crashed Ark. He subsequently defected to the United States and told them about Cobra's robot warriors...so, of course, the authorities treated him like a lunatic and threw him in jail. Until Cobra's robot attack on Washington, D.C., at least. He was released to join the newly formed G.I. Joe team, which he told about Cobra's planned attack on the SPS Center. He accompanied the team to the SPS Center, and encountered the Destro-controlled Laserbeak.
Mercer then journeyed to Cobra Island with G.I. Joe, where a virus had released all of the Transformers, Autobot and Decepticon, from Cobra's control. After capturing some Cobra troops with Sci-Fi, Mercer and the Joes confronted Megatron. Mercer became the first victim of the Decepticon tyrant's power when he was incinerated by Megatron's fusion cannon.