Floors 9 and 10 of Ancient Ruins are rather difficult instances. This is mainly because the boss's Landslide skill now increases the energy consumption of your Saints. The following lineup, however, can clear this floor rather easily.

1. Lineup: Chameleon June + Sextans Luna + Scorpio Milo + Gemini Saga + Eagle Marin + Kraken Isaak

Milo, as your main damage dealer, should be level 70+ and your other Saints should be at least 5 Star, level 60+ with around +4 Cosmo. All Saints should have [Tenacity] of at least +4 so that you can survive the onslaught. For other Cosmo, well, the stronger the better. For Saints that are not yet well trained, you can use Mandala to increase their survivability, and your team should have at least one Marsh Fairy.

2. Legendary Cosmo

Equip June with Mandala to increase her survivability, Luna with Marsh Fairy to generate energy, Milo and Saga with Chain of Hephaestus to increase their damage, Isaak with Equinox Flower to increase the HP of his tentacles, and Marin with Laurel Tree to increase her healing.

3. Battle

June links everyone together to share any damage taken. This spreads the damage to increase your entire team's survivability. Luna blesses Milo in the first round to enable him to dish out damage faster. Saga can use basic attacks at first, and then switch to his AoE skill once the Ancient Colossus splits. Marin casts her AoE healing every round before the split, so be sure to always leave her some energy. Isaak just uses his basic attack.

Attention: The boss will increase the energy consumption of your whole team. You will have enough energy on the first round, but you'll begin getting starved for energy on round two, especially since you have to use Marin's AoE heal every round. Therefore, Milo is the ideal Saint for these two levels due to his zero-energy damage dealing skills.

4. Replacing Saints

1) June can be replaced with other supports such as Cassios, Crow Jamian, etc. It should be fine as long as aren't losing Saints every round.

2) Luna and Isaak can be replaced with Cepheus Daidalos, Pegasus Seiya, etc. Seiya can apply weaken to the boss, making it take more damage and splitting sooner.

3) Milo is necessary to deal damage. If you don't have him, consider using Scylla Io instead. This way, as long as you summon Scylla in the first round and keep it from dying, you can rely on it to deal damage without spending energy. It is recommended to max out all of Io's skills. With its 280% increased damage, Scylla is able to make the boss split quite fast. Pisces Aphrodite is also a good choice due to his zero-cost damage-dealing skills.

4) Saga can be replaced with any other AoE damage dealer such as Leo Aiolia, Phoenix Ikki, etc. You need AoE mainly for taking out the small statues after the boss has split.