Crystal Catacombs is a 2D platform action game with RPG and roguelike elements. Players control Captain Vasil Ravencraft in his quest to defeat the Destroyer at the Crystal Catacombs. The game is divided in five different Crystal Realms, each with an unique setting: Keepenstein, Lost Jungle, Ice Fortress, the Pitt and Deep Darkness. Each realm is divided in five procedurally generated levels, with a mini-boss at the end of the third level and a boss at the end of the last one. The levels are comprised of rooms connected by corridors that can be present in any of its four walls. The goal is to find the exit room and unlock the gate with a key that can be found by killing monsters. Each level has a treasure room where items can be found. These items can be new weapons, spells, health or magic vials, temporary invincibility, among others. Gold can also be collected from enemies, some levels have a shop room where items can be bought. Every level has at least two teleport rooms that can be used to fast travel after two of them have been discovered, and some levels have a teleport room that will send the player to a random room where all monsters must be killed and a treasure collected before the player is sent back to the level they were at.
Vasil has a life meter, a magic meter and an experience meter. When the experience meter is full, a level is granted. With each five levels advanced, the player receives a point to be spent in one of four stats: health points, magic points, attack or defense. Vasil also starts with a sword that has an experience meter filled by use and can be upgraded up to three levels. Other weapons and spells can also be leveled up.
The game features four different difficulty levels: Normal, Hero, Rogue, Survival. The gameplay changes depending on the difficulty selected. In Normal players start with five lives, unlimited continues and can select realms in any order, with the difficulty increasing per realm. Hero differs from Normal in having less lives (three) and harder enemies. Rogue is even harder, with realms order predefined at the start of the game, three lives and no continues. Survival has a random string of levels, with difficulty increasing per 5 levels, only one life and no continues.