
If they see a new target with the same priority as their current target, they keep attacking their current target. Once a minion has chosen a target, it only switches to a new target if the new target has higher priority.
Enemy champions attacking an allied minion. Enemy turrets attacking an allied minion. Enemy minions attacking an allied minion. Enemy minions attacking an allied champion. Enemy champions attacking an allied champion. When minions find several enemy units they choose their target using a priority system that follows this order: Champions aggro enemy minions when they attack a nearby enemy champion with basic attacks, targeted abilities or spells. When they find an enemy unit, they attack it. Minions walk along a lane until they find an enemy unit. Middle lane minions are ghosted for 18 seconds. Top and bot lane minions are ghosted for 28 seconds. The very first minion wave is ghosted for a few seconds: After the 25 minute mark, one spawns every wave. After the 15 minute mark, one spawns every two minion waves. For the first 15 minutes, one spawns every three minion waves. They do not spawn on lanes on which super minions are spawning. If all the allied inhibitors of a team are destroyed, two super minions spawn on each lane for the enemy team. If one of the allied inhibitors on a lane is destroyed, one super minion spawns for the enemy team on that lane.
Each wave comprises several types of minions, which spawn in this order: Minions start spawning from the Nexus at 1:05 and keep spawning in waves every 30 seconds for the rest of the match. Howling Abyss Gameplay - Summoner's Rift Minion waves