Where can you use the fossil in Pokemon sapphire?

You can use the Fossil in Pokemon Sapphire to revive a Pokemon at the Devon Corporation.

Here's how it works:

1. Obtain the Fossil: You'll find the Fossil in a cave in the Jagged Pass (north of Slateport City).

2. Go to Devon Corporation: Located in Slateport City.

3. Talk to the scientist: There's a scientist inside the building who will revive your Fossil for you.

The Fossil will revive into one of two Pokemon:

* Lileep: If you have the Old Amber fossil.

* Anorith: If you have the Old Sea Fossil.

Which Pokemon you get depends on which fossil you have. Make sure to pick up the correct fossil before going to Devon Corporation.