The Storm Serpent is a super-heavy grav-tank of the Eldar that uses the same chassis as the Scorpion. It's another Eldar vehicle that has yet to receive an update since Second Edition. While other Eldar super-heavy tanks are noted for their immense firepower, the Storm Serpent actually contains a mobile Webway portal which it can use to disgorge warriors right into the enemy's midst, making this the Eldar's version of the Land Raider.
While the Storm Serpent superficially appears like a sleek gunship with a hull too small to carry any troops save for the pilot and gunner, the secret behind its function lies within the Wraithgate generator it carries. The Storm Serpent uses the same vast energies to power their immense weaponry in order to rip open a portal from the Webway, the Storm Serpent is able to create a shimmering portal amidst the craft's attuned promontories. This mobile portal can be accessed by the Eldar from anywhere, whether an orbiting fleet or Craftworld, for the rapid deployment of troops. The Storm Serpent could even summon a Vyper but no larger than it since the Wraithgate portal is ludicrously small to compensate for the practicality of use for the Storm Serpent without turning it into a static and glorified teleporter.
Due to its main use as a troop transport, the Storm Serpent sacrifices the majority of its internal bulk for the portable Webway device and thus is only able to mount a Pulse Laser and Scatter Laser for offensive firepower.