Reaper

Of all not-beasts, Reapers are the most feared. They began life as bears, already formidable and dangerous. After being infected by bloodsap, their aggression and power only gets worse.
At first glance, one could be mistaken for a very large bear. They still have clear signs of what they once were in their general body plan. The main difference is their size; they can easily grow to be twice the size of a grizzly bear. Their other most distinctive feature are the long, scythe-like claws that grow on their forelimbs and are the source of the name.
They have less thick fur than bears, and thick, leathery plates cover their backs to create a natural armour. The plates get thicker and more extensive as the mutation progresses, so that Reapers that have been infected for decades are armoured like tanks. Their ears become longer and more pointed, their teeth larger and sharper, and small bony ridges grow in over their brows that protect their eyes.

If you see a Reaper while scouting:

• Conceal yourself behind a boulder, tree or bush - downwind if possible.
• Do not make any noise
• Do not attempt to flee. It can outrun you.
• Do not attempt to climb a tree. This will cause motion and noise, drawing its attention. Reapers can climb trees.
• Do not attempt to fight it. Fighting a Reaper should only be done in a large group.

If you are lucky, you will evade notice by the Reaper. Wait ten minutes after it leaves your sight before moving. If the Reaper notices you and attacks:

• Aim for the joints under its belly where it is unarmoured.

If you are lucky, you will wound it before it kills you and make it less likely to take interest in any comrades in the area.

— From the Border Rangers' training manual.