This is a 360 card cube. Draft 3 packs of 15 cards from a singleton cube as normal, but you build a 60 card deck. You can include up to 4 copies of any card you drafted in your 60 card deck. The extras will be provided after the draft.
The goal is to create both a unique and high-powered environment. Cards that are legacy staples but can't quite make it in a cube due to density issues can be used here. It also allows for more interesting and niche archetypes, specifically tribal. Humans, Faeries, Ninjas and Zombies can all be supported within a cube for once, and it doesn't require bending over backwards to use 'bad' cards with those creature types to do so. 4 Gravecrawlers goes a long way, as do 4 Spellstutter Sprites.
Took a quick look at some common modern and legacy decks. Added a bunch of cards that require 4x to be good but once there can be really fun to play with.