Here are things that you should do on extra maps,and other stuff:

Extra Maps(after beating the game):

Extra Map 6:Before beating Sienna(AKA:SCARLET THE BRAVE),steal her
soul saber thats currently level 477 with a high level bottle mail
because she will give you a weaker version of her sword.

Extra Map 8:Steal Myao's catnip cane since thats the only way to get
it.There are no other ones,even in dungeons.

Extras:

Tutorial Map 3:Dont listen to what the computer says and confine a
bottle mail you got on Phantom Isle to the sword on that map because
this is the only way to get that sword.Good weapon for Ash in the
beginning of the game = D

Phantom Isle Secrets:Jump on top of the big high tree next to
Marona's home to get a change book.Stack 4 phantoms on that tree and
climb them to get a bottle mail!

Map 1-3:After defeating the boss on this map,go back there to see 2
owls,owl sentry and owl knight,on the left side of Marona.Defeat
those 2 to be able to create them!They will be gone if you return to
this map again,whether you defeated them or not.

Map 2-2:After defeating this map,go back there to see a owl mage
replacing the funguy.Defeat it to be able to create that owl mage!
The owl mage will be gone if you return to this map again,whether
you defeated it or not.

Map ?-?:On one of the later maps in the game,you will see dead
knights in the corner.Revive them and kill them again to be able to
create knights!

Dungeon's:

Enemy Types-
Male-Fighter,Blacksmith,Titlist,Mystic,Dungeon Monk,Knight

Female-Valkyrie,Fusionist,Witch,Healer,Merchant,Archer,Amazon

Feeble-Titlist,Old Man,Granny

Puny-Soldier,Putty,Slime,Whisp

Warrior-Fighter,Valkrie,Mystic,Knight,Soldier,Owl Knight,Owl
Sentry,Owl Ninja,Boar,Amazon,Merman,Putty Monk

Mage-Witch,Healer,Owl Mage,Owl Sage,Mermaid,Putty Mage

Artisan-Blacksmith,Fusionist,Titlist,Dungeon Monk,Merchant,Putty
Shaman,Putty Smith

Beast-Manticore,Fenrir,Hell Corgi,Giga Beast,Cerberus,Behemoth

Giant-Dragon,Golem,Manticore,Fenrir,Hell Corgi,Giga
Beast,Cerberus,Behemoth,Werewolf,Lizardman

Creepy-Zombie,Lady Zombie,Golem,Cerberus,Behemoth,Mimic,Lizardman

Horror-Zombie,Lady Zombie,Cerberus,Ghost,Whisp

Owl-Owl Knight,Owl Sentry,Owl Ninja,Owl Mage,Owl Sage

DemiMan-Boar,Merman,Mermaid,Scrabbit,Saber Kitty,Werewolf

Furry-Scrabbit,Funguy,Saber Kitty

Putty-Putty,Putty Monk,Putty Shaman,Putty Mage,Putty Smith

Slime-Slime,Shade,Mimic,Blob

Common-Boar,Merman,Mermaid,Zombie,Lady
Zombie,Slime,Shade,Mimic,Blob,Ghost,Whisp,Scrabbit,Saber Kitty

Shroom-Funguy

Weird-Funguy,Bottle Mail,Prinny

Various-#4-7 enemies will appear