Zubat.
Nothing but Zubat.
You can't do anything with altering cave unless you have an E Reader.
Nothing.
altering cave,
North in six island.
Six island its in the north.
In there you can only find zubat but the reason why its called the altering cave is because you can change what appears inside using a E reader device and E reader cards.
You can catch a Houndour in the Altering Cave in Pokemon FireRed.
Probably.
It is a mysterious cave filled with Zubat. If you did something with the Mystery Gift and a Wonder Spot, there would be 8 different Pokemon found there, but Nintendo hasn't yet done anything with it. In summary, it's useless (unless you need a Zubat).
In Pokémon FireRed, the Altering Cave is located on Seven Island. You can access it by using Surf to reach the small island situated to the southeast of the main landmass. Inside the cave, you can encounter different Pokémon based on the time and day, as well as some unique Pokémon not found elsewhere in the game.
Inside icefall cave.