The Reservoir is the third area accessible within the Lunar Soul Castle.
This area is mostly a light blue in color, with a lot of water. There are multiple exits - Reservoir L goes to the Laboratory, while Reservoir TL and Reservoir TR go to the West and East Tower, respectively. In addition, Reservoir SP leads to the Myst Zone, but only under special conditions. The Warp Doors can be found at Reservoir SP, and a few can be found at Reservoir B as well.
- Life Capsules: these only appear outside of 3-HP mode. In 3-HP mode, they don't appear at all.
- One is found at Reservoir I. It increases HP by 3.
- One is found at Reservoir LC, and increases max HP by 4.
- One is found at Reservoir O, increasing HP by 3.
- One is found at Reservoir S, and it increases maximum HP by 5.
- Mana for the Acidic Bubble Spell: treasure chests containing these can only be obtained when the spell is learned.
- A treasure chest increases the mana for it by 20. It is found at Reservoir B, and is the one of the ways to learn the spell.
- A treasure chest increases the mana for it by 15. It is found at Reservoir Y, and is the one of the ways to learn the spell.
- Air Tank: obtained at Reservoir B, underwater.
- Life Pot
- Beast Fang
- Weapon Shield: obtained in Reservoir I.
- Cure-All: found in Reservoir SP.
- Misery's End: obtained on the Reservoir Boss 1 map. Obtaining it will also start the boss fight against Irving.
- Bubble Key: obtained at Reservoir TR.
- Squid Medal: obtained after defeating Micren without taking any damage.