There are four Domains in Beyond the Veil, each corresponding to the various psychic, emotional, and alchemical properties inherent to the spiritual and mortal world. While Rank is the measure of how powerful a character the Domains a character possesses determines what sort of individual they are, and thus the character’s Attunements are a good indication.
A character may never buy a Domain rating higher than their Rank. If their Rank is reduced extra levels are suppressed and cannot be used. The exception to this is “bonus” ranks granted by Attunements.
A character is limited in how many Domains they can purchase ranks in by their Rank. If the character has purchased Ranks in too many Domains for their current Rank (such as when circumstances force Transubstantiation to a lower Rank) the character’s “extra” Domains are suppressed in order from lowest to highest rating (the character must choose which is suppressed if there is a tie).
Improving a character’s rating in a Domain costs a number of Souls equal to the new level times the number of times a Domain of that level has been purchased. Thus a character with Cups 3 who wants to go from Coins 2 to Coins 3 would need to spend 6 Souls.
When purchasing a new level in a Domain, the character receives a free Power from that domain of equal or lower level.