regular pokemon cards Deoxys Normal Forme | Diamond & Pearl—Legends Awakened guaranteed authentic card. Pokémon card types guide -

Three coloured mana is uncomfortable but easily supportable with cube mana bases, certainly mine

The only reason to play Mermaid Shimmer over Smokey Spirits is if you are running a torrential river deck, in which case the draw and damage dealing from Torrential River might make Mermaid Shimmer worth it over Smokey Spirits

Walk-In Closet / Forgotten Cellar is a Room, which is a modal Enchantment

Something like having a 5 mana scry for 2 on a land would rarely be activated and thus rarely worth it over the basic land unless it had no drawback at which point it would see play everywhere with no reason not to

The Gengars, Haunters, Mimikyus, every ghost-type Pokmon flying under the headline

If none did, the ability won't trigger at all