Name: Angus Mhor
Died: September 21, 1745 at PrestonpansAngus is a fairly major character who appears in all of the episodes in the first season and several episodes in the second season.
He was with Dougal and company when they picked up Claire near Craigh na Dun. In the cottage where Murtagh and she met up with the rest of the band, Claire told Angus to give her his belt for Jamie to use as a sling, and he was shocked that a woman would order him about.
Later at Castle Leoch, Angus and Rupert were tasked to follow Claire around and keep an eye on her (supposedly reporting her actions back to Dougal). We don't know much about Angus other than he's not very friendly towards and resents having to follow her around, especially if it keeps him from having fun.
On Claire and Jamie's wedding night, Angus and Rupert barged in on the couple, at Dougal's command, to see if they'd consummated the marriage. After they did, and Jamie went downstairs for food, Angus said to him lewdly, "If ye've worn Jamie out a'ready, I'll be happy t' take 'is place!".
Angus is the person in the TV show who taught Claire how to use a sgian dhu to kill someone (S01-E08 Both Sides Now), although in the book, it was Rupert.
In the book, Angus is the one who gives Jamie the beating (he took for Laoghaire), although in the TV show it was Rupert.