Puck

Puck is a deceptively cute yet terrifyingly powerful entity serving as the Great Spirit of Fire and the fiercely protective, fatherly mentor to the half-elf Emilia. Though he spent centuries searching for her, their true story began roughly seven years prior to the Royal Selection when he broke his original vows to unfreeze Emilia from the Elior Forest, forming a deep spiritual contract that required him to seal his own memories to protect her fragile psyche. Despite normally manifesting as an innocent, nine-centimeter-long, silver-grey cat with a gold earring and a tiny messenger bag, Puck is actually one of three ancient "Artificial Spirits" created 400 years ago by Echidna, the Witch of Greed, making him the spiritual older brother to Beatrice. Under his strict contract with Emilia, he is bound by rigorous constraints to conserve his massive mana consumption; he can only physically manifest during the daytime hours from 9:00 AM to 5:00 PM, must remain within ten meters of her, and will revert into a spiritual core when his energy drains. In battle, Puck manipulates temperature via "Fire Magic"—which paradoxically manifests as freezing ice shards, absolute-zero blizzards, and advanced Yin magic like Shamak—making him capable of easily slaughtering entire groups of witch cultists or massive demonic beasts. However, his most terrifying aspect is his hidden identity as the apocalyptic "Beast of the End"; if Emilia is ever killed, Puck's contract dictates that he must destroy the world, triggering a horrific process called "Star Beastification." In this state, he morphs into a monstrous, 20-meter-tall giant beast that mindlessly and aggressively drains all mana from the surrounding atmosphere, plunging the entire continent into an inescapable ice age that freezes every living being to death, a grim fate Subaru witnesses firsthand across multiple failed timelines. Recognizing that his overprotective nature and the mental seals of their contract were actively crippling Emilia's emotional growth and preventing her from passing the Trials of the Sanctuary, Puck made the heartbreaking, selfless decision to forcefully break his contract and vanish. This forced separation shattered Emilia's emotional dependency, allowing her to finally confront her traumatic past, regain her lost memories, and pass the Trials independently. Following the contract's dissolution, Puck lacked a sufficiently high-grade magical gemstone to anchor his consciousness to the physical plane, forcing him into a deep, silent hibernation inside a fragile, low-quality glintstone crystal, leaving Emilia and Subaru on a continuous quest in later story arcs to acquire a flawless, high-capacity magic crystal powerful enough to safely awaken him once again.