We just got a new Thunderbird in X-Men #100. Now we get his origin story.
I wonder why Claremont went through such effort to have six months pass, allowing him to introduce new characters and plotlines “in the middle”–so that the reader would have to wait for answers, just to drop one of them in an anthology issued just a few weeks later? That said, this is a good story to put in an anthology title that is not dependent on continuity.
His story is that he was kidnapped by Bastion as part of Operation Zero Tolerance. Kidnapped with him was his lover, Detective Karima Shapandar.
She got turned into an Omega Sentinel by Bastion. As Bastion was about to do the same to Neal, his latent mutant powers manifested and he escaped.
Then Jean tracked him down and invited him to join the X-Men.