In rare cases a special rule or Ability will cause an AI to Attack another fellow AI that might be a Swarm Monster. Since Swarm Monsters can reflect multiple figures using one card on the Initiative Track you might need to determine who to attack within that Swarm since they are all tied on the Initiative Track.
In these cases they target starting with the lowest number available to attack first.
(I.E. If AI is instructed to Attack a fellow Cave Sickle, it will Attack Cave Sickle 1 first, followed by 2 if Cave Sickle 1 is either dead, not on the board, or is in fact the figure making the Attack.)