Diane is a member of the Seven Deadly Sins and is The Sin of Envy with the symbol of the Serpent. She is also a member of the Giant's Clan.
She is a fair maiden with pink eyes and medium length brown hair which is tied up into Mega Twintails. Despite being a beautiful looking maiden, she is in fact a giant from the giant clan, and is several times larger than ordinary humans. She wears a one piece orange suit, boots that extend almost up to the knees, and a metal armband which is embedded with shiny metal pebbles. Her current outfits and attire is believed to be the most fashionable ones. She wears an orange colored short sleeved bodysuit and boots.
As the Serpent's Sin of Envy, her main traits are jealousy and envy. She shows strong affection for Meliodas, so when she met him together with Elizabeth, she grew very jealous and threw him away whilst calling him a cheater. In contrary with Elizabeth who wants to be strong and powerful, she wants to be small.