Hoenn walkthrough section
Pokemon Ruby and Sapphire Phase 7: Gym Strategy - Tate And Liza, The Psychic Leaders
Mind Badge Tate and Liza use Lunatone Lv. 42 and Solrock Lv. 42 in a double battle. Their reward is the Mind Badge and TM04 Calm Mind.
Phase 7 Mind Badge Lilycove, Mt. Pyre, villain hideouts, Mossdeep, Tate and Liza, and Dive. 07 / 10 
Phase 7 section 7 of 8
Tate and Liza use Lunatone Lv. 42 and Solrock Lv. 42 in a double battle. Their reward is the Mind Badge and TM04 Calm Mind.
Gym Strategy - Tate And Liza, The Psychic Leaders
Tate and Liza use Lunatone Lv. 42 and Solrock Lv. 42 in a double battle. Their reward is the Mind Badge and TM04 Calm Mind. The Mind Badge lets you use Dive outside battle once you receive it.
Gym Leaders
Tate And Liza, Mossdeep Gym
This is a double battle, so spread damage and partner safety matter. Surf is great if your second Pokemon can survive it.
Surf is the obvious button, but remember that it also hits your partner in Gen 3. Pair Surf with a Pokemon that resists Water, has high special bulk, can Protect, or is disposable under your ruleset. Dark moves, Ghost moves, Grass moves, and Water moves are all useful.
Do not bring two Pokemon that both fold to Psychic. If Lunatone or Solrock gets time to set up or spread status, the fight becomes more annoying than its two-Pokemon roster suggests.
Dex quick links