1 - Open Energy Gate (requires 2 energy).
2 - Save your game at the Spirit Well and teleport to "Thornfelt Swamp".

3 - Spirit Well.
4 - Ginso Tree's entrance, enter.

A17: Secret Area #6 at the top-right of the first section.

5 - Use Charge Flame to destroy the stone. Secret Area #7.

A17: Secret Area #8, it is a hidden path you can double jump to passthrough to the room above. It's a dead end though.

6 - Spirit Light Container, also  Secret Area #9, use double jump to reach it. I always forget about this one for some reason, I think it's very easy to miss, so watch out for it.

7 - Enter the bottom portal, then push the wood to the bottom.
8 - Use it to redirect the projectile to destroy level one wall, after that, push the wood into the portal.
9 - Enter left-bottom portal, then jump to #9. Push it to the bottom under the the enemy's projectile. Wait until the projectile teleport to level two and destroy the last wall.
10 - Kill the enemy in the room to open the door.

11 - Keystone, use portal and double jump to pick it up.
12 - Keystone, use portal and double jump to pick it up.
13 - Keystone, be careful because the surfaces will break when you stand on them.
14 - Keystone.
15 - Open Spirit Gate (requires 4 Keystones).
16 - Obtain Bash Skill from Ancestral Tree Reem.