All castles in Heroes 3.

Air magic reigns supreme! The chain lightning spell deals the same damage back as it did before the mirror, but in reverse. If (these numbers are just for example) it hits four units with a strength of 4/3/2/1, it will return with 1/2/3/4. However, the mirror often doesn't save you, and the attack goes through to your units. In my version, lightning also hits a maximum of 5 units, but Solomyr's version hits 6, and if you hit the central unit, the chain lightning will go in different directions.