"Purrjinn are magical genies. They are bottles brought to life by a mysterious god who just really likes cats. Because of this, they look like cats. Their body (bottle) contains their magical essence."

"To make a purrjinn, the Purrjinn God first creates a bottle as a seed. Once made, a bit of magic in instilled into an object and sealed inside the purrjinn. The purrjinn then awakens and begins its life."

Purrjinn do not age and are essentially immortal; as long as there is magic in their bottles they will continue to thrive. Purrjinn do not eat or reproduce (and as consequence do not have genitalia). Their glass-like bodies are made from a nearly unbreakable magical material, however breaking is possible. If cracked, the purrjinn must quickly be resealed with a magical bandaid to prevent loss of magic; this purrjinn however will become weaker.

Purrjinn are tricksters, and while they do not grant wishes, they may well say that they do.

(source)

Erlen's vessel happens to be an Erlenmeyer flask, filled with a glowing green slime. His tail, seemingly a tentacle of billowing smoke, is still soft and fluffy to the touch. His face and limbs are that of a light brown cat, with a bright green tongue and four brown eyes—one normal eye on the right, and a cluster of three smaller eyes on the left. The bands connecting his limbs to his glassy torso appear to be made from thick green glowsticks—that never lose their glow.

• Contents: Green slime (common)
• Bottle type: Bottom heavy (uncommon)
• Tail: Unique - Tentacle (Rare)
• Other traits: Extra eyes (Mutation)

Erlen typically wears a simple white, hip-length labcoat, and custom goggles matching the peculiar layout of his unique eyes, usually pushed up on top of his head.