The Arcane gate is the system used to buy things with points, such as the contents of Vaults and Grimoires, as well as Augments and Abilities.
“Magical Guardians are rewarded with “points” for a variety of activities such as defeating Anathema, completing quests, and saving people from danger. With these points, you can access what is called the “Arcane System” and purchase everything from spells and abilities to more mundane physical items. Clothes, weapons, and technologies from beyond your imagination are now a simple expenditure of points away!” Selene ch.3
Vaults:
Are catalogs of physical items such as clothes, weapons, and equipment etc. that once unlocked with points give access to purchase the items within.
Grimoires:
Are catalogs of spells that once unlocked give access to purchase the spells within.
Currently (ch. 37) the only known Grimoire is Mai's Grimoire of the Lonely Moon she got as part of her starting bonus for being a Dark.
Zero-Point Purchases:
“There are some items the Zenith deemed too important to the survival or well-being of Magical Girls to put a price on. They are considered a rite of passage among higher level Guardians. Because most zero-point purchases mean a truly desperate situation, having had to make one is a badge of respect.” Selene ch.20
Known Zero-Point Purchase Items
Purchases inside Usurpations:
“when you summon, you actually use some of your mana to send the ‘message’ of what you need. For lower tier items, it doesn’t amount to much more than one or two mana per summon, but some of the more advanced technology or more expensive items can take a healthy chunk. Basically, the mana you spend is used for punching a hole through the Usurpation zone to get the item sent to you.” Error ch.16
Rarity Levels:
An MG's tier is equal to (their level - 1)/100 rounded up, so tier 1 is levels 1-99, tier 2 is 100-199, etc. The highest level MGs are currently in the 500s, so are tier 6. An MG can only access items up to their current tier.
Common = Tier 1
Rare = Tier 2
Masterwork = Tier 3
Arcane = Tier 4
Legendary = Tier 5
Mythic = Tier 6
[Common is the first tier, then Rare, Masterwork, Arcane, Legendary, and Mythic. There is also a second set of tags used for more… esoteric items. The Arcane System, while useful, also has some oddities. Magic is not something that can be entirely codified or neatly labeled, and as such, the System sometimes does surprising things in its translations. The esoteric rarities are used to help label such idiosyncrasies.]” Selene ch.5
(At one point there were two higher tiers; since no current MG has access to these, Mika deleted them in an edit.)
Other information:
If a purchase is a physical object it will always come in a box except for objects being teleported directly into a MG’s body like soul gems, or if the MG has certain skills.
Points for a kill only go to the MG who has the final hit unless the participants are in a party. This is unlike experience, which the system splits up according to its evaluation of contribution.