Maglir is a bosmer knight and member of the Fighters Guild. He has an attitude problem and can be encounterd in Anvil, Bravil, Leyawiin, and Skingrad. Over the course of the game it becomes painfully clear that Maglir is not Fighters Guild material.
He can most often be found hanging around the West Weald Inn complaining about the Fighter's Guild. While in the Guild he repeatedly defaults on contracts, claiming the pay to not be worth the risk and having a family to think about.
The first contract he defaults on involves retrieving a diary from Fallen Rock Cave which he quickly offers to you. With diary in hand you can rat Maglir out to Modryn Oreyn and he'll refuse to help you out later on or give it to him. If given the diary he'll act like it's nothing and continue to complain about the pay but will be grateful to you and assist you later on.
You are teamed up with Maglir by Azzan to investigate a gang of bosmer thieves causing trouble around Anvil and kill them.
The second contract defaulted on has you finding him at the Lonely Suitor Lodge in Bravil, now a member of the Blackwood Company. Again you must complete his contract.
After joining the Blackwood Company, under cover and learning thier 'dirty secret' you must kill the hist tree. After doing so Maglir will appear enraged at you for taking everything away from him and attempt to kill you.