The only known info that can be confirmed is what Scrider really is. Scrider in Gunz The Duel, is "The Demented God of Destruction" confirmed by the description of the Scrider Premium Armor set. He is the only quest boss of "Legendary" grade, and is supposedly the final boss of Gunz. The sacrifice item's used to fight Scrider are Scrider's Registery Volume I + Scrider's Registery Volume II. No known way of obtaining these item's have been� confirmed yet, but is mostly likely obtained through previous boss's.
Scrider's stage has not been confirmed at all, however, rumor's have said his battle take's place in the "Stairway" stage, with 2 area's before you encounter him consisting of the "Lost Shrine", and "Factory" stage's. His rumored HP and AP are 6000/6000. He is rumored to having only 3 attack's, 2 only named, which are "Methor", and "Deathcall". His ability "Deathcall" is rumored to being a 1,000 Damage dealing attack, leading to an instant death to any player. Following "Deathcall" it is rumored it target's a specific player at random, followed by a long casting time.