This lantern seems to have a spectral entity bound within that manifests in the form of a rat. This lantern provides light like a normal lantern.

Once per long rest, a character attuned to the lantern can use their action to call forth a Swarm of Rats to their aid. The swarm follows the stat block within the Monster Manual but its appearance may change based on location and environment. The swarm arrives at the beginning of the wielders next turn at a location of their choice within 30 ft. and obeys all commands given to it by the wielder of the lantern.

When a rat swarm is within 5 ft of the character that is attuned to the lantern and that character is subjected to an attack requiring an attack roll, the character can use their reaction to cause the rat swarm to briefly move into the characters space and intercept the blow, using a Rat Swarms AC and HP. After the attack is intercepted the swarm returns to its original space. The rat swarm lasts for 1 minute or until it's HP is reduced to 0.

The Lantern of the Rat Lord can also be used to ritual cast the spell; Find Familiar. When the Lantern is used in this way, the holder does not need to provide the material components and the familiar must manifest in the form of a rat.