A seemingly normal rat enters the arena. How close to appropriate that appearance is depends on the phase of the moon. For now, intimidated by the charging monkey, the rat double-moves 30' north.
The light in the arena is artificial, so unfortunately the moonrat cannot benefit from natural moonlight, regardless of the phase.
I will assume the rat is at position 85N0E based on your move. It is allowed to enter the arena anywhere it wants on the western edge, not just the center.
The rat delivers an even more vicious bite! (Rolled 22) 1 point of damage. The monkey has 2 hp left.
Round 4:
The rat dodges the monkey's bite! (Rolled 12)
At this point the monkey just plans to bite the rat indefinitely. If the rat doesn't plan to change its strategy, I will time compress this combat and roll until one of them dies.
Indeed, the simpleminded (albeit horribly evil) rat is in the fight of it's life. There is nowhere to hide, nor any other obvious recourse. Her intellect precludes the subtle. To the death!
All of which is an overcomplicated way of saying, "Compress away!"
A horrible accumulation of knotted branches and roots that vaguely approximates a humanoid form enters the arena and charges at the simian before clawing at it with a sharp-ended branch oozing with black sap!
The owl tries a dive attack into Twiggy's square. Since the owl is above it and Twiggy doesn't want to jump, Twiggy will take the AoO first, then the readied action.
Twiggy misses the AoO! (Rolled 4 touch attack)
Twiggy misses the readied action! (Rolled 6 touch attack)
The owls tears Twiggy a new branch! (Rolled natural 20) 1 point of damage! The twig blight has 2 hp left.