Equinox’s first appearance is in the Batman: The Brave and the Bold episode Mystery in Space! where he captured Gorilla Grodd because his plans, as Equinox put it, "...would disturb the equilibrium." Equinox also captured The Question who, like Equinox, was trying to stop Gorilla Grodd. The Question inquired his reason for doing so and in answering The Question's inquiry, Equinox stated, "To keep everything equal of course. If I eliminate the black pawn a white one must go too. It's an essential part of my quest to bring the world into complete balance." Equinox dangled the two over a fiery pit on a large weighing scale; The Question tied to one of the weighing pans and Gorilla Grodd to the other. Batman appeared and Equinox triggered the scale to lower his captives into the flames. Batman rescued The Question and in effect, correspondingly saved Gorilla Grodd's life as well, but did not cut his bonds. Equinox fled the scene as Batman and The Question gave chase. Batman caught up with Equinox and they quarreled, but Equinox escaped and exclaimed, "Don't worry Batman. When the time is right, you will again meet Equinox!"
Equinox returned in the episodes When OMAC Attacks! and The Fate Of Equinox!
As the agent of both the lords of order 'and' chaos he has access to both their magics. He exhibits abilities to control time and space, i.e. turning a batarang into an actual bat or bringing stone statues to life. In other cases he can manipulate his powers to control the environment around himself subtly, making it appear like random chance rather than his manipulations (i.e. A branch breaking off a tree and falling into Batman's way just before he hits Equinox.).
His costume is black on one half and white on the other with a Taoist Taijitu on his chest. The Taijitu is a symbol that originated in the Chinese philosophy of Taoism and represents the concepts of yin and yang which have the characteristic of balance and are complementary opposites within a greater whole. As his name and costume suggest, he has an obsession with balance. He maintains this obsession through his actions, making his alignment of being good or evil highly questionable. His only known motive is, as Equinox himself put it, "...to bring the world into complete balance."