Oskar Tyre and the other founding members of the Jadame's Temple of the Sun had traveled from the temple in Antagarich to share their scripture. Their leader was a man called Brother Howe, but he was slain by Regnan pirates on the way.
Tyre had a holy vision had led him to declare war on the Necromancers' Guild, as he wanted to rid Jadame of their activities. However, the undead hordes were numerous, and the war wasn't going as well as he had hoped. He'd sent one of his clerics, Dyson Leland, to disguise himself as a Necromancer and spy on them, but Dyson was discovered and forced to serve them.
When the Hero of Jadame asked Tyre to join the Alliance of Jadame, he asked the hero to contact Dyson and get him to help them enter the Necromancers' Guild and destroy the skeleton transformer. However, the alliance was also trying to get the Necromancers' Guild to join, so the hero had to choose which side to ally with.
Oskar Tyre can be found in the Temple of the Sun in Murmurwoods. He gives the party the Destroy the skeleton transformer quest, which must be completed to have the temple join the Alliance of Jadame. After this, Tyre can be found in the Merchant House in Ravenshore.
Oskar Tyre appears in Might and Magic VIII: Day of the Destroyer.