Arlin and Extra Dungeon:
Beat Amalgam and save the cleared data. Load it up and go to your base and trigger a scene. Then go to Luda's Playground and use the Float ability to find a new portal which is upon a boulder next to the SouthWest entrance. Once withinside Mull's Dungeon, you will also encounter Arlin to rejoin your party.

Get Norm's Illusion Attack:
After the test in the Playground, put all the purple pieces on all the squares so that they are on all 4 corners as well as the center.

Delsus Spirit Attack:
Go and talk to the old man in Lake Forwell and give him a Gogo Suit and Snickerdoodle.

Klein's Living Item Attack:
Speak to Zeldalia and she will give you the choice between Living Item or Mana Item. You will be able to get the other later.