Tales of Phantasia [GBA]

Unlockable Dungeons
After you have revealed Dhaos' Castle in the future, two new dungeons will be unlocked.

Dwarven Ruins
In the Treasure Room of the 21st level of Morlia, there is a blue button that you can press to reveal a warp for a new dungeon. Dungeon has 9 floors.

Morlia Mineshaft (Lower Levels)
After you have revealed Dhaos' Castle, head to 9th floor of the Morlia Mineshaft, now there will a new opening for 12 new floors (21 in all).

Ishitori Sequence
Whenever you play Ishitori with the Ishitori Master in Alvanista Castle, go first. Then Always bring down the amount of stones to whatever number is closest in this sequence
1-5-9-13-17-21-25-29-33-37-41-45-49-53-57...etc.
You will win every time.

Optional Summons
There are several summons that can be obtained without going through the game, but doing certain other sidequests in the future after you have obtained the Tech Birds.

Chameleon
Get the Emerald Pact Ring from Gnome's Cave in the future and then make it to the 16th floor of Morlia Mineshaft, he is in a room filled with gas.

Gremlin
Get the Sapphire Ring from Undine's Cave and reach the 21st level of Morlia. He is in a room located in the south with gas.

Pluto
Go to the Dwarven Ruins, obtain the Lapiz Ring there, and make it to the 9th floor to have a boss battle with Pluto/Brute.

The spirt of Darkness, Shadow
Go to Lone(Sylph) Valley and get the pact ring from the catacombs, then go to the cave of darkness to the southeast of Arlee.

The spirt of Light, Aska
Go to Alvanista and talk to the lady standing at south entrence, then go back to the time machine in Thor and ask for Aska to be released.

Unlockables
Battle Lv.3 (Maniac) Difficulty - Beat the game once.
Mini-Game - Let's Go Arche - complete the game once
New Game+ Mode - complete the game once
Pink Options in Title Screen - complete the game once
New Songs in Sound Mode - complete the game once (Japanese version only)