Here I will tell you how to open 2 inaccessible characters.
Guide to Open All the Characters
How to Unlock Pandora
Pandora is a healer magician.
To open Pandora, you need to complete the game to level 10 and defeat the boss, then use the orange exit instead of the usual one.
How to Unlock Bastion
Bastion is a melee berserker that stuns opponents.
To unlock the Bastion, you need to accumulate 10 omni stones, (they are transferred to other games, even if you exit or die) and then find the Hammer of Dawn at the location (where the hammer appears is unknown. I met 2 times in the forest) and activate it by spending 10 omni stones.