Tree strikers are semi-intelligent, carnivorous monkey-like
creatures. They have short black fur, long, clawed arms, a prehensile
tail, small heads and a small mouth full of razor-sharp teeth. They
inhabit dense forests and hunt in packs, and prefer to hide in
low-hanging tree branches and drop on unsuspecting victims while
hanging from their tail.

They are only about three feet tall when standing upright, but have
long arms that reach to the ground and a tail that is at least as long
as they are tall. This gives them quite a reach when hanging from
trees - even a branch 12 feet or so in the air would allow the tree
striker a solid hit with his claws on a passing human-sized
creature. From a greater height, the creature will drop onto a
victim's back and spring away after the surprise attack, eventually
making it back to the trees and allowing their hunting companions to
also attack. They will return for more attacks if they sense a weak or
frightened victim or victims. They surprise 1-3/1d6, except against
Rangers or Wardens, who both have their normal chance of being
surprised in the wilderness.

Tree Striker*

+--------+----------------------+
|AC      |7 [12]                |
+--------+----------------------+
|HD      |1+1                   |
+--------+----------------------+
|ATK     |1d6 claws/1d3 bite    |
+--------+----------------------+
|SP      |Surprise attack from  |
|        |above                 |
+--------+----------------------+
|MV      |12/24 ground/tree     |
+--------+----------------------+
|HDE/XP  |2/30                  |
+--------+----------------------+
|SAV     |16                    |
+--------+----------------------+
|ALN     |Chaos                 |
+--------+----------------------+
|ENC     |2-12                  |
+--------+----------------------+
|ML      |9                     |
+--------+----------------------+
|BHB     |+1                    |
+--------+----------------------+

* Stat block above is for Swords & Wizardry Whitebox (or OD&D, Delving
  Deeper, etc.), where HD are d6-based. For other S&W editions, or for
  Labyrinth Lord, use 1d8 for both HD and damage.
.