Steel Shade is a boss that appears in the Dimensional Vortex.
Steel Shade is a Shade version of Crono. Despite the fact that his techs have different names, the effect is the same and seems to have Crono's strongest equipment available in the game. Most notably is the resemblance between his weapon and either the Rainbow or the DreamSeeker.
It is highly recommended to wear the White Vest and White Plate against Lightning elemental attacks in this battle. Scintillation, a magical attack that gets cast halfway through the battle, is just as powerful and looks exactly like Crono's Luminaire. Like Luminaire's damage multiplier and Prism Spectacles equipped (Ayla can and should Charm this rare item), the spell can dish out a lot of damage, potentially killing an unprepared player. The rest of Steel Shade's attacks are not as threatening.