Drown the unbelievers in a sea of blood!
Henzell says...
  1. Mechanic to discourage {pillar dancing}. If 1) you move away from a hostile monster within its melee range, and 2) it moves toward you, and 3) you're in melee range again, then it gets a 1/3 chance of launching a "free" attack against you (which can miss as usual). Terms and conditions in following entries. See also {energy randomisation}.
  2. Doesn't apply if the monster is confused, incapacitated, fleeing, unable to see you, delayed (eg due to a slow ogre swing) & unable to follow you, self-destructing (eg ballistomycete spores), OR if you're doing a Wu Jian martial move or Serpent's Lash.
  3. Attacks of opportunity mostly work like normal attacks, but in 0.30 and prior, they couldn't trigger some special effects that caused bugs, eg phantoms' AF_BLINK_WITH. Reaching monsters (eg polearm monsters) didn't get reaching opportunity attacks, just the usual ones from adjacency.
  4. Monsters also may randomly lose a small amount of energy when when they perform an AoO.

Information based on master branch and the great LearnDB.
© Dungeon Crawl Stone Soup, 2010.