Sir Ocelot and Professor Penguin are exploring a newly discovered cave system and competing for precious gemstones found inside. To locate and collect gemstones, players use tools — compasses, lamps, and pickaxes — and their trusty companion's good instincts. Gemstones, geodes, celestites — the deeper the rivals go into the cave, the more valuable the treasures to be found!

To set up Sir Ocelot's Cave, place the amethyst tokens for each of the three cave levels into their appropriate bag, then randomly place the level 1, 2, and 3 cave tokens on the empty spaces in the appropriate levels. Each player starts with a companion and a set of fifteen double-sided tool tokens that have different tools on opposite sides.

Each turn, place one of your tokens — either tool or companion — on the game board. Your companion can be placed on an empty space or a 1-point gemstone in level 1, while a tool can be placed on any empty space on the perimeter of the cave or between levels of the cave. (Once your companion is on the board, at the start of your turn you can move it up one level, again placing it on an empty space or a 1-point gemstone.)

After placing a tool or your companion, check to see whether any cave token is "seen" on three different sides by all three tool types. (Your companion counts as a tool of your choice.) If so, you claim that token by removing it from the board. If you collect a geode or a complete set of celestites, you draw a random amethyst tile from the bag matching the appropriate level. Each amethyst has a fixed value or scores based on the cave tokens you collect or the cave tokens left behind.

Once both players have taken sixteen turns and placed all of their tokens, the game ends, and whoever has the more valuable collection of gemstones wins.