A six-foot tall, bald, gray-skinned humanoid with black eyes tumbles into the arena to 80n25e, swinging a black-bladed katana. Baldy casts pain, holding the charge in one hand while wielding the katana in the other.
Round 628: A 15 foot long eyeless yellow-green pterodactyl flies to 55N80E20Z. It has a large fin on its back and a single horn protruding from its head.
The birdie does not come down to get touched. Instead, it turns and flies to 90N45E20Z, and sends a ray of sonic energy at Baldy, hitting him (29 ranged touch) for 23 points of sonic damage. Baldy has 22 HP remaining.
Well, that answers the question of whether or not Birdie can see Baldy. Baldy will stand there and ready to teleport to 0n115e should Birdie attempt to send out another ray.
Sorry about that. I had thought that Baldy made his presence known. Birdie did not notice Baldy, and flies around waiting for its opponent to show up. Baldy is at full HP.
No, I didn't specify -- actually, I didn't know I should specify -- so I think by default Baldy would make his presense known. After all, how could he otherwise cast pain on Birdie?
I think the default is that his presence is not known, but I had the idea Baldy wanted his presence known.
Given your clarification, Baldy is at 22 HP. Birdie circled around in round 630.
Round 631
Birdie circles around again and sends out a ray, which misses because Baldy is now at 0N115E. Birdie flies some more, turning toward 0N115E, and is at 40N85E20Z, SE.
Birdie lands at 5N100E and bites Baldy (rolled 32) for 12 points of damage. Birdie grabs Baldy (39 vs. 17 grapple) in its mouth, pulling Baldy into its space. Baldy has 10 HP remaining.
Note that Baldy's teleportation ability is spell-like, not supernatural. His Concentration modifier is not high enough for it to be possible to teleport away.