A biome which is found by descending naturally, and separates levels.
Each Holy Mountain will contain one full health restore, a spell refresher that will refill your spell uses, a shop where you can purchase spells or wands, a small room containing the Worm Crystal, and lastly an altar with a handful of perks to choose from. There are also two large pools of water next to the health and spell restore, which can be useful for cleaning your cape or refilling flasks.
On the right side is a tunnel leading to the next area. Upon exiting, the ceiling above the perk altar will collapse and physically block the passage. Red particles will appear and deal significant damage to the player if they try to re-enter the room (though these fade away after a short time in proximity)(Trying to enter the Holy Mountain by teleporting will result in a death by "Holy Mountain curse"). Additionally once the ceiling collapses, you will be unable to edit any wands in the last holy mountain.
Other Important Information
The Mountain is made of material that is resistant to explosives but can be destroyed by other means such as acid or Worms. If the walls surrounding the inside area are damaged sufficiently, the player will receive a message saying "You have angered the gods" and a Stevari will henceforth spawn inside the perk room of every Mountain in the current run. This will sometimes only occur when the player enters the Mountain through a tunnel created in this way. Note that this only applies to the shop area, and the player can safely dig the brickwork to the sides of the shop with the right spells or acid to travel up or down levels if needed without angering the gods.
Though there are many portals at the end of each area they all share the same exit, as there is only one Holy Mountain per level. Entering a second portal on the same floor will not refresh the pickups or shop inventory. Sometimes the portals are submerged in a liquid such as blood or lava.
Upon destroying the Worm crystal in the room underneath the shop, a message will appear saying "You feel less safe." and the Mountain will no longer be protected from worms.
The full health restore also grants ten additional maximum health points, even if the player has Glass Cannon (although picking up any 25+ HP pickups will revert the max HP back to 50). To the right of the perk altar there's a scale used for perk rerolls. The starting price for a reroll is 200$ and it doubles in price every purchase (200$, 400$, 800$ etc.). Rerolling allows the player to stack perks making their effects stronger.
If the player makes it to a Mountain without killing anything directly in the previous area, a Chest will spawn on the perk altar.
It is possible to leave a Holy Mountain and return later with more gold for rerolling perks or shopping. The climb back up the exit tunnel can be achieved using polymorph, teleportation, low gravity/strong levitation, or a wand with strong knockback. If there is a ledge close to the tunnel, such as in Hissi Base or The Vault, the tunnel can be ascended by simply pumping the levitation on/off to maintain upwards velocity while conserving fuel.
Polymorph can be used to safely exit the Mountain without triggering the ceiling collapse. This also allows one to return and edit wands later—just be sure to Polymorph on the way back in as well.
If the player picks up a perk from the perk altar, blood will flow from the glyphs of the altar. If the player didn't kill anything in the biome before the Holy Mountain, water will flow from the glyphs.