Mythic Booster Box
The Mythic Booster Box is the top rung of the personal booster box ladder — a step above the Legendary Booster Box on both axes, and the only one that isn't bought or crafted.
Open it and you get one booster at random from the same four picks every booster box uses: ore, shard, energy, or XP. Whichever you land on runs at 2.5× for 60 minutes.
Where it sits on the ladder
| Box | Multiplier | Duration |
|---|---|---|
| Common | 1.25× | 30 min |
| Rare | 1.5× | 30 min |
| Epic | 1.75× | 30 min |
| Legendary | 2× | 30 min |
| Mythic | 2.5× | 60 min |
Every other tier runs 30 minutes; Mythic doubles the clock as well as raising the multiplier, which is what earns it the tier.
Where to get it
Uber bosses only. All four of them — Uber Lamia, Uber Echidna, Uber Thanatos and Uber Hephaestus — drop it, and it's the bulk line on every one of their tables, so it's the thing you'll see most from an uber kill. Nothing else in the game pays one.
Stacking
Only one personal booster runs at a time, so activating a Mythic replaces a Legendary you already had going rather than stacking on top of it. Save it for a clean start.
It does pool with a Global Booster, though — personal and global add together, so a Mythic alongside a Legendary Global Booster is 3.5× for the hour. That's the current ceiling.
Boxes stack in your inventory, so you can bank them for a mining session rather than burning them on the spot.