Haak Trobis was a Starfleet veteran, originally from the planet Daran V. Blue-skinned Trobis had previously served aboard a Constitution-class Federation starship.
In 2267, terminally ill and trapped in a sealed life-support suit, Trobis helped hijack the USS Enterprise at the command of a fellow Starfleet Veterans' Hospital patient named En-Lai, but Kirk suspected that Trobis would be granted clemency for the crime. When En-Lai diverted the Enterprise to Calydon, Trobis's illness was completely healed by the lady of Calydon. (TOS comic: "A Small Matter of Faith")