Dark based equipment is mainly found in Legaia 2: Duel Saga. Legend of Legaia's only Dark based accessories are the Ebony Jewel, Dark Stone, and Dark Talisman. In Duel Saga, Dark equipment ranges from weapons that add the Dark element to attacks, to armor that reduces damage against Dark, to collectibles that have to do with the element itself.
In Legend of Legaia, Dark summon spells are best used by Vahn. Nighto is the earliest Dark Seru that can be obtained and summoned, followed by Puera. The most powerful summon spell is Jedo's Deadly Promise. The magic effect of Dark element summons is a reduction of the targeted enemy's MP.
Legaia 2: Duel Saga utilizes no Dark element summons.
Multiple enemies in Legend of Legaia and Legaia 2: Duel Saga use Dark based attacks. The boss characters in Legend of Legaia are the primary users of Dark element attacks, due to Dark being strongly associated with evil.