Lightning-X Istros I4 is a Hasbro Exclusive Energy Layer released as part of the Burst System as well as the SlingShock System. It debuted in western countries with the release of the SlingShock Single Pack Lightning-X Istros I4 4 Accel-S.
Lightning-X Istros I4, as its name implies, is a SlingShock-Exclusive variant of Istros I2 that's reclassified as an Attack Type Energy Layer. However, despite the "Lightning-X" prefix and "I4" suffix, Lightning-X Istros I4's design is unchanged from its Dual Layer counterpart, and the only difference between them are their color schemes. Unlike the color scheme of Istros I2, Lightning-X Istros I4's color scheme consists of a translucent-yellow top-layer with black paints apps on the wings that have the appearance of lightning, a blue bottom-layer, six neon-green designs in the center that have the appearance of thunderbolts, and two heads facing forward on either side; with both of their heads colored blue, their eyes being yellow, and their armored helmets having silver paint apps. Unlike all other SlingShock-Exclusive Dual Layers, Lightning-X Istros I4 does not feature glitter of any kind that's infused into its translucent plastic. Aside from this, like all other SlingShock-Exclusive Dual Layers, the "I" in the center of the Lightning-X Istros I4 is transparent while the rest is colored green. Aside from the absence of glitter, these details enforce the "Lightning-X" motif of the Layer's prefix, but not for its "I4" suffix. Like Istros I2, the heads of Lightning-X Istros I4 appear to have no connection towards any mythological being.
For more in-depth information on performance, one should refer to the Istros I2 page.