Fels is an immortal being over 800 years old, originating from the ancient magic nation of Altena. Once celebrated as "the Sage," Fels mastered the rare development ability "Mystery" and became history's sole creator of the Philosopher's Stone, an artifact granting eternal life. However, the ritual backfired, consuming their flesh and transforming them into a living skeleton. This event caused profound self-loathing, leading Fels to abandon their title and refer to themself as "the Fool." Physically, Fels appears as a skeleton shrouded in black robes, making their gender indeterminable. Possessing Level 4 adventurer status grants them enhanced physical capabilities surpassing lower-level individuals. Their combat prowess includes proficiency in concurrent chanting—casting magic while moving—and wielding potent magical artifacts. Key development abilities are "Mage," amplifying magical power to rival a Level 5 caster, and "Mystery," enabling the creation of advanced magic items unmatched even by top crafters like Asfi. Signature magic includes "Dia Panakeia," a potent healing spell comparable to elixirs that cures wounds and nullifies curses, and "Dia Orpheus," a resurrection magic that succeeded only once in reviving the Xenos Wiene. Fels serves as the clandestine agent of Ouranos, the Guild's leader, operating from the shadows for centuries. Guild staff occasionally call them "the Ghost" due to rare sightings in the headquarters. Their duties involve intelligence gathering, such as investigating incidents like the food storage crisis on the 24th floor. Fels initially resisted aiding the Xenos—intelligent monsters emerging from the Dungeon—but grew to champion their cause, believing coexistence with surface races requires conquering the Dungeon's deepest levels. This conviction drives their guidance of Bell Cranel, whom they mentor to embrace being labeled a "hypocrite" for pursuing just ideals. During the Xenos crisis, Fels facilitated alliances between Bell, Ouranos, and the Loki Familia. They intervened to rescue Xenos captured by the Ikelos Familia and provided sanctuary in Knossos. Despite setbacks, including Hermes's manipulations that nearly doomed the Xenos, Fels trusted Bell to achieve the impossible. This culminated in Fels performing "Dia Orpheus" to revive Wiene, reinforcing their faith in Bell's potential. Later, Fels participated in the Knossos raids, dismantling magical barriers and transforming the labyrinth into a workshop to support exploration efforts. Fels's artifacts demonstrate unparalleled ingenuity. Notable creations include "Occulus" crystals for long-distance communication, "Magic Eater" gauntlets firing shockwaves, "Reverse Veil" cloaks granting invisibility, and "Illusion Flower" pollen inducing hallucinations. Their "Seeker Powder" locates targets via blood samples, while golems serve as formidable guardians. A familiar owl equipped with an Occulus eye aids surveillance, underscoring Fels's role as a strategist and inventor. Personally, Fels balances wisdom with dry humor, occasionally making "skull jokes" while reacting sharply to being called a skeleton. They harbor trauma over their immortality experiment but remain confident in their magical and tactical acumen. Their bond with Ouranos is built on centuries of mutual trust, and they fiercely oppose those exploiting the vulnerable, such as Hermes. Fels's legacy endures through their guidance of heroes and unwavering commitment to a future where humans and monsters coexist.