Crown Vault

You can access this area by fully charging a Proto Statue, which will spawns a green portal leading to the vault. The portal spawned after taking a crown leads you to the third level of the area you were previously in.

The first time you enter all you will find here is a Crown Pedestal. Taking the Crown will create a portal which allows you to leave. What type of crowns you get depends on if you looped the game. You can also choose to not take a crown at all.

If you enter the Crown Vault the second time, or if you started the run with a crown, the Crown Pedestal will be guarded by two Vault Statues. The third Vault will have the Crown Pedestal and four Vault Statues. Each Vault Statue spawns a Crown Guardian which you have to kill before leaving the vault. Destroying the Vault Statues before reaching for the Crown will prevent you from being able to get a new crown or return the current one in this Crown Vault, even if you defeat the Crown Guardians.

Entering the Crown Vault more than three times per a single run is not possible, as Proto Statues will stop spawning after you visit your third vault.

A Proto Chest will spawn inside the Crown Vault if you already have a Crown when entering it.

Each time you exit a Crown Vault the game's difficulty is increased by one, meaning that better weapons have a chance to spawn earlier, but there are more enemies.

Trivia

 * The main theme for the Crown Vault is "Vault".
 * The boss theme for the Crown Guardian is "Guardians of the Crown".
 * If an alternative soundtrack plays in the game (aka B-Track) and you enter a Crown Vault in the same run, the Vault generates with a few floor tiles that have pictures on them. It's unknown in what order they should be looked at and what exactly they are portraying.