The Radio Tower will look like this from the front.

Upon entering the front entrance, you should see the floor 1 lobby.

At the front desk in the lobby, you should see a Grunt. Behind him are some lattices you can break to reveal hidden barrels. The middle one contains a Corrupted Shard. Keep hold of this - you will need 8 of them.

There is an opening on this floor which looks like a waiting area. Inside is a Team Rocket Agent and a chest with some mints.

This waiting room has a door, which opens to a room that looks like where news anchors would sit.

Back to the floor 1 lobby, there is a door which opens to a room with quartz blocks for walls.

Behind the iron door in the quartz room is a Team Rocket Officer.

Past the crimson doors next to the Team Rocket Officer is a library.

In the back left corner of the library, there is a lever behind a trapdoor.

Pulling the lever opens a secret room with a chest. Inside is a Corrupted Shard.

Back inside the floor 1 lobby, there is a door behind some lattice.

Inside, you can find the lab, with a Team Rocket Scientist and a dragon egg.

Close to the door that you entered, you can find a barrel underneath an anvil. You may need to break some blocks to get to it. Inside the barrel is your 3rd Corrupted Shard.

Remember to check all of the blast furnaces. Some of them contain fossils.

In that same room with the Corrupted Shard and the Scientist is a door behind lattice.

Inside the back of the lab, you can find some barrels on a shelf. These contain valuable items like mints, TMs, pokeballs, and more.

In a corner, you can find the setup for spawning Mewtwo and other Fossil Pokemon. Be sure to steal it if you don't already have this.

Back to the floor 1 lobby, go up the stairs. At the top, you should see Apollo.

Beating Apollo gets you the Shadow Heart. Make sure to loot the chest behind him and the pot close to him - there are 2 Trial Keys there.

Next to Apollo is an open room that looks like another waiting area.

At the end of the room, the end sofa can be broken to reveal a lever.

Pulling the lever reveals a room behind the plant. Break the plant to get in.

Inside the hidden room is a Team Rocket Spy. Also a chest with a Corrupted Shard.

Don't forget to break the painting, revealing another hidden barrel.

Back inside the 2nd floor waiting room, climb the lattice in this corner and break the chimney.

Inside is a maze with obsidian walls. Apologies for the dark image.

If you don't want to play with the maze, you can break all the obsidian. Otherwise, a tip is that redstone torches mark dead ends.

You can also mark off dead paths to save time like shown in this guide.

Somewhere in the maze is a room with another Corrupted Shard. Behind the lattice is a barrel with ancient debris.

One of the dead ends has a lantern, which is hiding a barrel with a Corrupted Shard inside of it.

After finding your way back, do not go up the stairs in the 2nd floor waiting room just yet. Go into this room with the Team Rocket Scout.

Behind him is the door to the second floor library. You can see the stairs back to 1st floor on the left of the image. Go into the doors on the right of the image (left from the doors you entered from).

You will come across this study. Loot the chests - one of them has a mega stone.

Using the desk trapdoor, you can go into one block height mode and get to the secret room behind the desk.

Lots of barrels to loot in this room. The left side table with the brewing stand on it has a Corrupted Shard.

Behind the lectern is a barrel with a Synthetic Matrix.

You can use the Synthetic Matrix with a Netherite Chestplate and Netherite Upgrade Template in a smithing table to be able to toggle between Mewtwo and Shadow Mewtwo.

Go back to the 2nd floor waiting room, then up stairs, down halfway, up the ladder, and you will meet Giovanni.

He drops a Silver Wing. Hold onto this - you will need it to summon Lugia.

Behind each of the statues in this room is a barrel you can loot. The one behind Giovanni contains the last Corrupted Shard. You can now craft the Shadow Soul Stone and have the ability to toggle Lugia between its normal and shadow form. This item has infinite uses.