Let's imagine we're back in the late 1980s & early 1990s. For most people, the largest thing they'll ever see in a game of Rogue Trader is probably a metal Land Speeder or plastic Space Marine Rhino or perhaps a Land Raider tank. Some ambitious folks might build a Baneblade using Tony Cotterell's templates
in White Dwarf 132, but that's probably your lot.
Enter then, Mike Biasi from the USA. After upscaling an Epic Titan to 28mm, Mike secured a licence from Games Workshop to produce a range of 40k vehicles based on the Epic designs under the trading name Mike Biasi Studios. Soon, other companies were in on the act, with Epicast, Armorcast and Forgeworld USA holding licences for various vehicles until Games Workshop set up its own in-house, large scale resin casting unit (Forgeworld).
The Eldar Tempest is unusual in that not only was it one of the largest non-titan kits produced, but that Mike Biasi's original sculpt was reworked and put into production no less than three times (Mike Biasi Studios, Forgeworld USA, Armorcast), over a period spanning at least 6 years!