|Treants||140||6||6||8||2 attacks, 2 damage, animate trees, fire vulnerability|
Treants: These are enormous sentient-tree creatures. At the start of a turn they can animate a section of woods within 6" range to join them; this creates a new unit with twice as many figures, fighting the same except for 3" move rate (use this ability only once per game). If attacked by magical fire, they receive no saving die.
Treants were a great challenge to price correctly -- I recently reduced them after a playtest, but even so, they're the highest-priced units in the game so far (and for the foreseeable future). They have excellent armor, pretty awesome attacks, very high hit dice (almost Hero-level), and the potential to effectively triple their starting numbers. However, this is offset by their slow movement rate, their vulnerability if the opponent takes a fire-using Wizard or Dragon, and the great gamble you're taking for a Woods tile to appear in range on the table (about 1-in-2, and so about half their value comes from the ~50% chance to animate trees).
A couple things that I considered but rejected (although you might re-institute them as variants): (a) Possibly simplifying the tree-animation to triple the size of the treant unit, instead of creating a new unit (this was discarded because slowing all of the treants to 3" would be a huge loss in attack potential); and (b) Enforcing a command/control requirement that the treants stay within 6" for the animated trees to remain active (a complicated kind of rule that I've avoided on principle for BOW, and would permit killing the treants to wipe out the trees as well, greatly devaluing them; contrast with 3E).
Consider altering the value for a campaign-game in which you have advance knowledge regarding the type of terrain in which they'll be fighting (i.e., if you're not using the standard Book of War random terrain frequencies): If you know that there will not be any Woods on the battlefield, then their value is only about 80. If you know there will definitely be Woods accessible on the battlefield (like in a deep-forest battle), then value is estimated to be about 220. (Possibly subject to future revisions -- tell me how they work out for you!)
[Illustration by ^Sandra^ under CC2.]