Diopside's corrupted form is that of a giant centipede-like creature. She is composed of roughly thirteen (visible) dark-green segments (excluding the head and the rear) that each bear one pair of similarly colored legs. The final segment bears no legs, but what appears to be a pair of mandibles. Each of these segments is covered on the top side with a solid crystal covering. Her head is composed primarily of a large pair of jaws/mandibles with a gem in the back of the "mouth". This gem is circular in shape and colored light green with dark green contour lines surrounding the circumference of the gem, connecting to a circular shape. Her gem seems to act as her iris, being in the middle of what would rationally be a sclera. It also features a green crystal protuberance on the base of the head that forms a broken horn-like structure. She has a flowing, light-cream colored mane immediately behind her head.
Once cured of her Corruption, her form takes on a far more human-like body type. Her main outfit consists of a standard Homeworld full body suit: a V-shape symbol reaching to her belt, both of which are dark green, with the rest of her suit a dark grey color. Her skin is a duller green, with her eye and hair matching her corrupted form. Her Gemstone has replaced her eye completely, working as if it was her true eye.
Diopside was at first a bit startled and nervous when she first returned to her non-corrupted form, but she soon began to calm down and shows a friendly sort of nature, especially towards Flint, Jade, and Steven Universe. As she was corrupted herself, she has shown a bit of resentment in fighting them, and sympathizing with them as to their condition.
Diopside was once a worker for Homeworld. It is revealed that she was also one of the gems working under Hessonite's control. She remained like this up to when she tried to help Jade and Flint escape. Unlike the two, she ended up captured, and as punishment for betraying Homeworld, she ended up Corrupted. She was then placed down onto Earth, where she was spotted by the Crystal Gems, and they proceeded to poof her and place her into the Crystal Temple. She was released later on at one point, Steven trying to befriend her, but she ends up poofed once again.
Her gemstone was found by Flint and Jade during their talk with Garnet, and she became the only Gem Nephrite was willing to heal. Upon being healed, she panicked and tried to get away, taking refuge on the Beach House's support beam. She accused them of trying to harvest her, but she calmed down on remembering Jade and Flint, along with Steven Universe. She was caught up on recent events with the Crystal Gems and the Mane Six, and explained her backstory to Steven. She and Steven were found by Discord, and agreed to let him stay a while after being bribed by Chaaaaps.
Her role from there is mainly as a side-character and supporter to many of the group's missions.
My Little Universe II
In "Child's Play", she is called by The Spirit to her realm alongside Star Quartz and Jade to talk about Discord and White Diamond's power. She tries to make a good case for them, but due to the Spirit's intervention during Your Great Honor's court session, she was refused any word in much to her anger and was forced back to her world. She finds out later about their duel with Your Great Honor, and tries to think of what to do about it. During this she got a future vision from Garnet, which ultimately helped her and her friends in the fight with Your Great Honor. In their fight, she was the first to see the source of his anger: a sword jabbed into the back of his neck. She, Jade, and Star get it out for him, as such winning the fight. While given the chance to get White and Discord's magic back, she reveals that it's only temporary, and decides to grant Quetzalcoatl his freedom back instead as exchange for helping Your Great Honor.
She joins the Harmony Gems in both the final court session with Discord and White Diamond and the final fight with Grogar's Army. Before the fight, she remains behind in the Realm of Corners to buy her friends time to destroy Grogar's ships. However, in the end she was captured along with the other Harmony Gems and Off-Colors, and brought onto the ships to kill them in front of Empire City. Lucky for her she was freed by the recovered Harmony Gems and with their help they stop Grogar's forces from leaving Homeworld.
Diopside's Gemstone, as it is apart of her eye, allows her to sees in a similar manor to a advance telescope, even able of adjusting the vision to see long distances. This advanced vision can see through areas normally visually meek for others.
An ability from both reformed and corrupted form, Diopside is able to generate highly corrosive acid from her mouth, which she can use as a biting attack. It is strong enough to melt away various materials, and actually poof a strong Quartz Gem. She can also generate this acid from her Gem eye.
An alteration of her acid can also be generated as a gooey, gel-like substance.