Players receive the hidden machine for Strength from one of the two old women on the fifth floor of the Lost Tower on Route 209. Players must first earn the Mine Badge to teach Strength to a Pok?mon, according to Bulbapedia.
Outside of battle, the move Strength is used to solve puzzles and push boulders that block your progress. In battle, Strength is a Normal-type move that inflicts damage and has no other effects. Once Strength is taught to a Pok?mon, it cannot forget Strength to replace it with another move, and it can only be forgotten by talking to a Move Deleter, as explained by Bulbapedia.
Like the Pok?mon Tower, the House of Memories and Mt. Pyre of previous generations, Lost Tower is a memorial and burial ground for dead Pok?mon. The wild Pok?mon you encounter in Lost Tower are primarily Ghost-type, and each floor of the tower is populated with gravestones. There are six Pok?mon trainer battles between the second and fourth floors of the tower, two of which are double battles. While the old woman on the left on the fifth floor gives you the hidden machine for Strength, the woman on the right gives you a Cleanse Tag, which lowers the encounter rate of wild Pok?mon by one-third if the first Pok?mon in your party holds it.