here ya go:
o get this epic follower you'll need a Level 3 Lumber Mill. To get the Tier 3 blueprints for your garrison buildings you will have to complete Upgrading the Mill, which includes turning in 75 orders in the Lumber Mill and completing Reduction in Force and Legacy of the Ancients.
After this you'll be able to log Large Timbers. Logging them will have Phylarch to spawn 3 times before he "surrender" and join your side, becoming one of your followers.
He can be assigned to the Lumber Mill as worker since he has the garrison ability Evergreen and there he will give Subversive Infestation.
source:
http://www.wowhead.com/follower=194....green#comments