Diane is the Serpent's Sin of Envy of the Seven Deadly Sins. Diane is a member of the Giant Clan and is thus much larger than ordinary people, including Diane fellow Deadly Sins. Diane Sacred Treasure is the War Hammer Gideon, which Diane uses in conjunction with Diane inherent power, Creation.

During the New Holy War arc, Diane 's strength was fully acknowledged by the former King of the Giant Clan, Drole as he himself died protecting Diane after declaring Diane as his successor, making Diane the next potential ruler of the Giants as well as the unofficial "Giant Queen." Diane is also currently the wife to King, who is the current King of the Fairy Clan.

As a giant, Diane is several times larger than an ordinary human being. Diane is a fair maiden, described as "lovely, beautiful" with purple eyes and medium length brown hair which is tied up into large twin tails. Diane has a well-endowed and curvaceous body. Similar to most of the other Seven Deadly Sins, Diane facial appearance is relatively childlike and has shown little change over the years. Diane's wanted poster depicts Diane with light-colored hair. Diane symbol, which is of the Serpent, is located on Diane left outer thigh.

When Diane was still a child, Diane wore ragged clothing until King made Diane a new set. Diane clothes during the earlier part of the series resemble what King made for Diane, having sewn it herself by using leather derived from Dusk Bison skin.[3] Diane earlier attire consisted of a short-sleeved one-piece orange suit, boots with five crossed laces that extend almost up to Diane knees, and two finger-less gauntlets of a blue-grey leathery material covered in shiny steel stud - with the right gauntlet having been destroyed by Gilthunder during the fight in the Forest of White Dreams. Diane also wore a backpack previously used by Meliodas. Diane wears a short purple sleeveless dress with white puffballs down the front while human size or the Boar Hat uniform while serving at the bar.

Ten years ago, Diane —as a Holy Knight— wore a full-body orange armor with a unique helmet like the rest of Diane fellow Deadly Sins.

After Hendrickson's defeat, Diane wears clothes made by King [4] that are almost the same style as Diane previous one, except for an inverted triangle cut on the chest and the skirt. Diane also wears black underwear resembling bike shorts underneath the skirt.

During the New Holy War, Diane wears new clothes made by Merlin.