The Tale of Jinchi
This is the wandering spirit of Abbot Jinchi (Golden Pool), who appeared in Chapters 16 and 17 of the novel, in the novel, he was a 270 year old Monk who was the head of the Guanyin (Bodhisattva of Mercy) Monastery. A covetous character, he lusted after Tripitaka's cassock, bestowed by the Buddha, and plotted to obtain it.
The cassock was the sign of Buddha's favor and was embedded with precious gems and relics that granted the wearer succor and protection. He persuaded Tripitaka to lend him the cassock overnight for viewing and Tripitaka relented. In the deep of the night, he plotted with his favored disciples, Guang Mou (Vast Schemer) and Guang Zhi (Vast Intelligence). Guang Zhi offered the plan to murder the pilgrims while they are asleep using swords and knives, but Guang Mou countered that it is easier to burn down the building Tripitaka was sleeping in. The ease of how they arrive at the plan makes you wonder if this is their first rodeo.
Wukong, already suspicious of the monks, stayed awake at night and became aware of the plot. He borrowed the Fireproof Mantle (Jinchi's drop after defeat) to shield the building, while maliciously fanning the flames to spread to the rest of the temple. In the end, Jinchi committed suicide after finding his temple burnt to the ground and the pilgrims very much alive. Guang Zhi and Guang Mou were assumed to have died in the fire.
In Black Myth Wukong, these two were instead agents of the old Lingxuzi and Whiteclad Noble, and escaped after the fire. Guang Zhi was overwhelmed with remorse for his actions, and actually set himself on the path of Buddhist cultivation, while Guang Mou became a Taoist master of poison magic. Jinchi's covetous spirit lingered due to his violent death and held on to the Fireproof Mantle that lead to his downfall.
In Chapter 1's ending cutscene, the Bodhisattva Guanyin was asked about the motives of Jinchi, despite being a high ranking monk of great cultivation, why would he still lust after the cassock, a material possession that only permits the cycle of desire to continue. Her reply that if he does not have the accoutrements that can display his eminence and the level of his cultivation, how would people know that he is a high ranking monk of great cultivation? I think this sets the tone of the world view of Black Myth Wukong, where the gods and buddhas have impure motives, authority and power is the ultimate arbiter of who is considered eminent and enlightened.