Inspired by a journey to to the east in 1925, the British artist Henry Baines began experimenting with the art of sand painting upon his return to London. His mandalas were greatly admired in art circles and he got around the problem of their impermanency by preserving them with photography. Many of these photographs he gave to friends or traded, and it was around this time that he came to possess a copy of The King in Yellow. The book inspired his sand art in a new direction, away from blatant Eastern influences towards a more surreal style. Many in-the-know note the increasing presence of the Yellow Sign, albeit stylised, in his later works. 

The title of this spell is a misnomer as the mandala can actually be comprised of many colours of sand (though yellow, black and grey are the most predominant), poured through a specially crafted chak-pur (a traditional metal funnel for creating sand mandalas). The Mandala can be as small or large as the artist desires but must be created within an enclosed area to be "consecrated." Meditating upon the Mandala opens a way for the caster to enter Carcosa.

After the caster finished meditating it will seem like nothing has happened, other than a slight drop in temperature. If there are any windows in the room then all that can be seen outside is fog. Moving beyond the confines of the consecrated area (such as through a door) will reveal the truth. Should the caster wish to leave Carcosa, they simply return to the area they consecrated and meditate upon the Mandala once more. No matter how deeply within Carcosa they may go, the caster is never far from the Mandala-room at all times and always knows instinctively how to reach it.

The Mandala's power is fragile and if it is erased before the caster has left Carcosa, they are condemned to wander its streets forever. Such was the fate of poor Henry, who neglected to lock the door to his studio one hot summers day. His new maid, who knew nothing of art but was eager to make a good impression on her new employer, gave his studio a good sweep and clean. At least that is the most popular explanation. The maid herself insists she left the room as it was; with the strange clawed handprint in the middle of the Mandala and the pile of white sand beside it.

Though this spell is rather unique, photographs of Henry's Yellow Mandalas are rumoured to still exist. A resourceful investigator or cultist who gets their hands on one, along with a special chak-pur of the sort Henry used, could recreate its effects.