How to reach the Tower of the Twelve Stars and contract with Luna.
How to Reach the Tower of the Twelve Stars
From Alvanista, go east and south, then east when you can, to find the dock to Freland. Go to Freland and go east past Olive Village, and go through the mountain pass to the east. Go northeast from the first oasis, then northwest from the second oasis, and finally north from the third oasis. Cross the two bridges and you will no longer be in the desert. Go northwest from there, and you will see a bridge to the west. Cross it, then cross the bridge just west of that, then make your way south to find a camp. Cless/Cress can learn a skill here. Then leave the camp and go north to those bridges. Cross them, then Go north until you encounter another river. Go north across that river, then go east and you will see Midgard. You can optionally go in and buy supplies. See the "Midgard" section of the Treant's Forest page for more details.
From Midgard, go west until you can go south across the bridge. From there, go slightly east and south to find a tower. Go inside.
Spells and Summons to Use
The Brigand enemies in the tower are immune to Arche's Thunder Blade and Eruption, so you might want to turn them off.
Floor 1: Capricorn and Aquarius
Go through the door, then in the next room, go up the stairs.
Floor 2: Pisces and Aries
In the middle of the room, there is an obelisk that tells you which background music must be playing for the door to the next level to open.
The correct music is playing now, so if you don't want any treasure, just go through the exit in the north wall. Otherwise, go south from the obelisk to exit the room. At the split, go west and into the first room to find a Spy Lens/Magic Lens, and go into the second room to find the Tractate, which is a weapon for Klarth/Claus. Then exit and go east, past the zodiac symbol on the floor, and go into the first room to get a Basilisk Scale and a Sage, and go into the second room to get an Apple Gummy/Apple Gel/Apple Gummi. Now go back to the obelisk room and use the exit in the north wall. Go up the stairs.
Floor 3: Taurus and Gemini
If you don't want the treasure on this floor, go south to the next room, and go into the second room on the left. Check the statue to make the music change. If you do want the treasure on this floor, go east from the obelisk room and go into the first room to find a Sage. Go back to the obelisk room, then south, and go into the first room on the left to get Bread. Then, in the second room on the left, check the statue and press the button. Then check the rightmost room to find a Holy Rune. Go back to the obelisk room and go west, and go into the second room to find an Orange Gummy/Orange Gel/Orange Gummi. Then, back in the obelisk room, exit north and go upstairs.
Floor 4: Cancer and Leo
For the quick way out, go west and into the second room to find the statue that changes the music. Otherwise, go east and go into the second room to find an Orange Gummy/Orange Gel/Orange Gummi in the left chest and a Charm Bottle in the one on the right. Go back to the central room and go south, and go into the rooms on the right. The first room contains a Protect Ring and the second room contains a Sirloin Steak. Go back to the central room and go west, and go into both rooms. The first room contains a Basilisk Scale on the left, and a Remedy Bottle on the right. Then go into the second room to find the statue. Then go back to the central room of this floor, go north through the door, then go up the stairs.
Floor 5: Virgo and Libra
If you just want to change the music, go south and enter the rightmost room, and press the button on the statue. If you want to get treasure first, go east and into the first room to get a Mantle. Go back to the central area, then go south and enter the first room on the left to get a Rabbit's Foot, then go into the rightmost room to find the statue and press the button on it. Go back to the center room, and go west, and go into both rooms, the first of which contains a Silver Cape, the second of which contains a Battle Rune. Then go back to the central room and go through the north door, then go up the stairs.
Floor 6: Scorpio and Sagittarius
If you just want to change the music, go east and enter the second room, and press the button on the statue. If you want to get treasure first, go east and into both rooms, the first of which contains a Rune Bottle, the second of which contains the statue. Then go back to the center area and go south, and go into the rightmost room, which has a Rabbit's Foot on the left and a Black Onyx on the right. Go back to the center room, and go west, and then go into the first room to get a Resist Ring. Now go back to the center room, go through the north doors, and try to go upstairs. When you can, go north to the next floor. Talk to Luna and you will forge a contract with her. After that, you can leave the tower. To do so, go south, and whenever you are in a room with an obelisk, go slightly southeast from the obelisk and go down the stairs there.
Optional: Purchase Tempest Skill
If you haven't purchased the Tempest skill in the Venezzia armor shop, you might want to do so now. Tempest requires mastering Lightning Bolt and Blade Storm. It is helpful to have this skill before the next part of the game.
Go to Midgard
From the Tower of the Twelve Stars, go north and cross the north bridge, then go east and enter Midgard.
The entrance to the castle is in South Midgard, in the upper middle of the area. Go up to the castle entrance and there will be a cutscene. Before you talk to Edward, you will have to wait in a room. Don't try to leave. Eventually, there will be a cutscene. After Lyzen and Edward leave, exit the room and go east, then north.
After the cutscene, you can talk to the people in the magic research center. Afterward, leave the castle. There will be a cutscene.
After the cutscene, go to South Midgard and enter the castle gates.
When you are back in control, buy supplies if needed. The Pharmacy is in the southeast, and the weapon shop is in the northeast. To the right of the weapon shop, there is a passage leading north. It goes to the north part of the city. The food shop is nearby, and the supplies store is above that. In an alley south of the supplies store, there is a man who will sell Cless/Cress a new skill for 18000 gold if you didn't buy it earlier.
When you are ready, go back to the castle, go upstairs, and go toward the conference room. You will then be sent to the Valhalla Plains.