There is no AoO because Howie had total concealment from the fog. That is why the bat lowered five feet -- so it could see Howie.
Howie hits with claw and bite, critically with the claw (highest missing roll was 23; lowest hitting roll was 25) for 21 points of damage. Batty has 35 HP remaining, and Howie got the crit he wanted.
Round 460: Batty bites back, bestowing 19 points of damage, and then 5-foot steps up to 40N55E10Z. Howie has 2 HP remaining.
Howie hits with claw and bite, critically with the claw (highest missing roll was 23; lowest hitting roll was 25) for 21 points of damage. Batty has 35 HP remaining, and Howie got the crit he wanted.
Round 460: Batty bites back, bestowing 19 points of damage, and then 5-foot steps up to 40N55E10Z. Howie has 2 HP remaining.