Adric is an undead human crossbow archer and an old friend of Garrick. While it appears he has gained his independence, he does not seem to be allied to the Forsaken and was able to infect his former friend with the Plague.
Wishing Garrick had not come to find him, Adric ends up shooting Garrick in the back when he tries to lead him to his cart to hope that his master could use Adric in able to find a cure for the plague. However, Adric does not want to be cured.
Whether these two are still friends living within the unnamed blighted forest is unknown.