I'm sorry, when I said "slithers as fast as it can", I meant it used the run action. Suprisingly, animated objects have a base speed of 40 feet, so the rope is already in the kobold's square.
Right...kobolds, not known for their depth perception, though the arena was 200'x200' not 120'x120'. With reality dawning, the kobold takes his AoO with the spear, then a 5' step to 5N 0E and attacks again.
The kobold has his sling out, so no initial AoO. The kobold drops his sling, backs up and readies his spear, and attacks.
Hits! (Rolled 19) 4 points of damage! The rope is destroyed and teleported away!
The kobold enters the Hall of Fame!
A 5-1/2 feet tall woman enters the arena. She is bald and her dull red skin seems to be glowing. She has ivory white eyes. She wears tight-fitting studded leather armor and wields a light steel shield. In her other hand is a strange 6 inch long weapon with a curved blade.
She runs to 5N30E while her skin comes to a full glow. The kobold is surprised by the woman's ability but not dazzled by the illumination. (Rolled 21 Fort save)