Some monsters are only unlocked in Grandpa's store if you have met specific criteria. For example, the Sinister Serpent is only available for purchase once you have obtained 50 Water-type monsters.
Win the game to get these cards at random.
Note: You only get 3 cards below each time you beat the game so you may need to beat it multiple times to get all the cards in the game.
This can only be unlock by doing certain tasks in the game. They can all be bought at Grandpas' Shop in Entrance Hall.
Unlockable Monster Evolutions:
To get more experience for a monster, have that monster destroy your opponent's symbol. They will get anywhere between 50 to 100 experience points.
Usually when a monster or capsule is destroyed, you cannot use it during the next round. However, if you start the next round and bring up the menu with "End Turn", "Unit List", etc. and go to "Surrender" and select "Try Again", you will restart the level with all your monsters available for use.
Certain map attributes can cause physical damage to your monsters, such as lakes of lava and crackling electrical arcs. Only monsters with the same attributes as these dangerous spaces can pass through unharmed.
You must have three Harpie Ladies in order to fuse the Harpie Lady Sisters monster. Because only two Harpie Ladies are available for capture on Mai Valentine's Valley of Howling Winds board (and never in the shop), you must play through the game twice to get all three.