Jovan’s team retrieved the Mask of Life from the chamber, and they brought the mask to Karda Nui. There one member of the team donned the Ignika and sacrificed himself to restore Mata Nui’s health. SOURCE: Jovan - BIONICLEsector01
So my theory here (since Jaller, Kongu and Matoro never had a combiner model like the other half did to make Jovan) is that the first Toa that saved the Great Spirit was indeed a Toa of Plasma that wore the Kanohi Iden.
It looks exactly the same as Matoro Inika but with silver armor from Kongu and trans orange from Jaller, not sure what kind of weapon he had (maybe a double-edged sword with a Zamor Sphere Launcher on the middle like Umbra did with the Rothuka?)