What content is there of Torgar?
Two main endings (corrupted and redeemed). Only the redeemed ending gives a new achievement, rewarding a Tonic that converts Corruption into extra stats in battle (only lasts a few expeditions). However, two glyphs can be gained early on costing essence, and an additional item in a more recent patch related to the Slime. Corrupted Torgar also give a unique buff that stacks five times with each encounter, but is easily overshadowed by other, far more powerful and exploitable buffs. Encountering Corrupted Torgar five times (getting the max stack) adds him to your party, and Redeemed Torgar is recruited in the next encounter after he's redeemed.
To be honest, he's perfectly skippable after doing the redemption path, though encountering him at least twice is recommended each reset thanks to the glyphs and the extra item related to the Slime (the latter can be purchased alongside the other glyphs for cheap, but only then). As a party member... he scales poorly after several resets, even with the new level upgrades added in recent patches that boost party stats. As far as I'm aware, only Kanathar scales well, since you can give him essence to boost him directly, though one of the new teammates (the before mentioned Slime) seems to have some potential.