Oldbark's Woods predates Titania's Kingdom. Oldbark himself has given conflicting accounts on how old he is (almost assuredly on purpose) to scholars who get the rare chance to interview him.
Located to the southwest of Titania's Kingdom the region is entirely made up of hardy trees creating a dense wood line that is hard to traverse. This is by design as Oldbark only allows those who pay his tax passage by moving trees.
Oldbark feels that Titania's Kingdom should be under his control as well. Frequently the two get into territorial disputes along the border. When a common enemy arises Oldbark will put aside his differences and help Titania (killing a Witch Of The Blackest Bog for example).
Oldbark makes a large sum of money off taxing travelers in his lands. Nobody is quite sure how much money he makes annually or what he plans to use it for. Given that most of the people who live in his woods are fellow ent's there is not a real economy to speak of.
Most sentient beings in Oldbark's Woods are fellow ents but on some very rare occassions Oldbark allows what he refers to as 'Fleshy Ones' to reside in his woods.