She's an ultra-powerful "Stone Cold Betty", that part's me...and she's, like, kinda tall — that part's Pearl.
—Amethyst, "Giant Woman"
Opal has bright-periwinkle skin, and thick, wavy, off-white hair. Her hair extends slightly past her calves, tied back into a rowdy ponytail by a pale salmon band. Extending from off the sides of the ponytail are two small pigtails in the front tied by pale yellow ties and chin-length bangs, which resemble Pearl's. Opal has a lean, toned body with two pairs of slender arms. Her face is thin and rounded, inheriting Pearl's pointed nose and Amethyst's plump lips. She has two gemstones in the same places where Amethyst and Pearl's gemstones are. Opal is very tall, being at least twice as tall as Garnet. Her height is partly due to her constantly being en pointe, meaning constantly on the tip of her toes. Her outfit consists of fuchsia, knee-length leggings with pale-violet cuffs rolled up, and yellow flat boots.
Opal had a pastel teal top with a drape in the front and back that went down to her shins, featuring an accented star at the base. The way she wore these drapes were similar to Amethyst.
As seen in "The Return", Opal had undergone some changes. She had a sash around her waist and an added neckline to her top. Her appearance changed in accordance with Pearl's regeneration in "Steven the Sword Fighter". However, since she appeared in white and green-tinted light, the colors of her clothing are yet to be confirmed. They are assumed to be the same, with slight differences.
As seen in "Log Date 7 15 2", Opal has undergone another change due to Amethyst's regeneration in "Reformed". The sash around her waist was replaced with a yellow waist base and light green design with straps overlapping the yellow part. Her neckline has also become a singular dark green color.
As seen in "Together Alone", Opal has undergone yet another change due to Amethyst's regeneration in "Crack the Whip". Her top is now ripped and exposes her waist. Her leggings are also now shin-length and more orchid, and her eyes are a sort of fuschia (instead of her previous sea foam colored eyes).
Opal is an amalgam of our combined magical and physical attributes fused into a single entity.
—Pearl, "Giant Woman"
Amethyst and Pearl are extremely powerful when they are willing to work together in the form of Opal. Amethyst's ability to live in the moment along with Pearl's obsessive single-mindedness results in a stable fusion. Opal achieves peace in that balance that Amethyst and Pearl rarely experience on their own. At times, Opal is so calm and at peace that it causes her to forget the task at hand (for example, forgetting to retrieve the Heaven Beetle after rescuing Steven). In addition, according to the book "Guide To The Crystal Gems", Opal is very forgetful.
The balance that holds Opal together is, by far, the thinnest of all the other known fusions. The ease with which Opal can separate is very different from that of Garnet, who is almost impossible to unfuse except under extreme emotion, or if by force (Ruby and Sapphire can willingly separate anytime they wish). If Pearl and Amethyst have conflicting views while fused, this can cause Opal to revert to her constituent Gems; the slightest dissonance between the two poses a danger of involuntary defusion.
Opal's personality is theorized to be a combination of Amethyst's power, along with Pearl's grace and decisive determination. She appears to be more open to Steven's desire to have fun and play, as she sang part of his song back to him. This is a trait that can be traced back to Amethyst.
In "Fusion", Opal shows both Pearl and Amethyst's personalities by posing with elegant and silly poses.
Opal possesses standard Gem abilities, bubbling, shapeshifting, fusion, regeneration, agelessness, and superhuman strength/durability.
Archery Proficiency: Opal's weapon is an opalescent longbow that fires arrows made of light-based energy. The bow is roughly as tall as Opal herself. She fuses both of her fusees weapons together to form her bow. Pearl's spear makes up the limbs of the bow while the lash of Amethyst's whip becomes the string. Her arrows are summoned when the bow is drawn back, currently, she has 2 types of arrows.
Gem Bubbling Arrows: These arrows form an alarm which can cause a large explosion which emits a bright light on impact, as well as bearing a striking resemblance to the energy blasts that Pearl's spear is capable of. Gems that are pierced by these arrows have their gemstone(s) automatically bubbled and teleported to the Burning Room.
Multi-Shot Arrows: These arrows also have the ability to split into multiple, smaller arrows that can attack multiple targets simultaneously.