Sins of the Prophets

Sins of the Prophets (SotP) is a fan-made total conversion mod created for the 4X real-time strategy game Sins of a Solar Empire, most prominently its Rebellion expansion. Developed by Slugfest Studios, SotP combines space battles involving dozens if not hundreds of ships with the fast-pace seen in the Halo games. Set during the late-Human-Covenant War, players are able to play as either the UNSC or the Covenant, with an asymmetrical balance to ensure that neither faction plays the same way.

History
SotP was originally founded at some point in 2008. They released their first beta for the Entrenchment expansion on Jan 17th, 2013, which consisted of only the UNSC faction. On July 22, 2014, they released a second beta ported over to the newer Rebellion expansion, which added the Covenant Empire as a playable faction.

In a Canon Fodder post from 2016, Jeff Easterling published an interview with Slugfest Studios in regards to their mod.