Map: Twilight Field
Recommended Element: Water
Heart Container: Lana
Heart Piece: Lana
Skulltula: Defeat 1,000 enemies
Take control of the nearest outpost then head to the southwest. Once the objective is updated, head there and rescue Agitha. After the cutscene, stick with Agitha and escort her to her destination. Once you've reached the Outskirts Keep, defeat the Dark Aeralfos to capture the Keep then continue forth afterward.
After the cutscene, Agitha will fall back to the village. Engage Midna's Forces and take control of the West Field Keep. This will display the Twilight covering the area. Take control of the outpost to the northwest. At this point, your main base will be under attack. Head over there quickly and take out the attacking forces to give you peace of mind.
The objective will update to defeating Midna. Before you do that, you're free to capture the other bases and outposes. This will remove the twilight on these shadowed bases, as well as weaken Midna. Removing the twilight on all bases will severely weaken Midna. Do this to your advantage. Midna's weakpoint will appear after she swings her summoned arms and sending out her panther. With all her twilight coverage gone, even your normal combos should hurt her enough that you'll defeat her without exploiting her Weak Point Gauge.
After the scenario, Midna will be unlocked as a playable character.