For details and such, Halo 5 Forge PC has a custom games lobby that me and my friends use to mess around and play fun modes like this! Mongoose sumo is a relatively self explanatory mode where everyone drives a mongoose on a platform that procedurally gets smaller, all trying to push each other off… Last person on the platform wins.
Hope you guys enjoy, heres the video: https://www.youtube.com/watch?v=U_60z_jxfDM