“The Fourth World” is the utopian group show at Arch Enemy Arts in Philadelphia centered around the concept of a secular paradise populated by fantastical creatures (“heaven without religion,” according to the gallery). The interdisciplinary artists in the show focus on character-based 3D work. There’s Erika Sanada (Hi-Fructose Vol. 31), whose dog sculptures examine animal instincts and impulses. Then there’s the delicate, taxidermy-like works of Caitlin McCormack; the ornamented bone sculptures of Chris Haas; Doubleparlour’s mutated creations and Adam Wallacavage’s tentacled chandeliers. While the idea of “The Fourth World” hints at an idealized wonderland, there are notes of darkness in many of the works. But for a group of artists with a penchant for surrealism, there’s really no other way.