Unlocks at 5 stars. Will be farmable from the Guild Event Store after he is unlocked at 5 stars. This event only runs for 3 days.
Requires the following characters, with at least 17,500 power:
Light Side battle (choose 4 with asterisks *)
Dark Side Battle (choose 4 with asterisks *)
This reddit post explains the gear requirements, omegas, & zetas needed to reach 17.5k on each character.
Star Forge Showdown returns tomorrow.
Showdown at the Star Forge is announced to start on 4/12/2019.