Despite the developer being done with it, they've expanded it again. Siralim Ultimate 2.0 is out now as the "biggest update ever". Even before this update the game was massive, and easily one of the biggest monster-catching games ever made. Now it's truly huge.
What exactly is it? Tough to pin down properly to a genre, because it blends quite a lot. There's monster catching, dungeon crawling and more with over 1,200 different creatures. The developer says to think of it like "Pokemon meets Diablo, or more accurately, Dragon Warrior Monsters meets Path of Exile". If you can appreciate the very retro style, there's a huge amount of depth to it.
In the new update they've translated it into 14 languages, there's various new game modes to play through from an Ironman Mode to a Calm Mode and more. You'll also find hundreds of new creatures, traits, spell gems, cards, and achievements.

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It has Native Linux support and Valve rated it Steam Deck Playable.