Two regions, one Size rule
The arena is not one flat field. You come out of the green portal into the jungle: dense, green, and where most players are. That means more food on the ground and more predators hunting it. Keep walking and the ground turns to snow. That region is the Tundra.
Official promo art matches those looks: palm rivers and waterfalls on one side, and a snowy conifer scene in a four-panel image. The art is advertising, not an in-game minimap, so do not treat a tree or a waterfall in the artwork as a labeled landmark.
A practical loop
- Eat in the jungle while your Size is low, because the food is there.
- If a Spinosaurus or T-Rex model is sitting on that food and its Size is higher, do not wait it out.
- Cross toward snow and keep eating.
- Come back to crowded food once your own Size is the one other players are avoiding.
Red damage means you are already in a losing trade. Biome hopping does not change who can eat you. Only the Size number does.
Codes are not biome keys
Expired code TUNDRA paid items, including a frozen Therizinosaurus name. That does not unlock the snow as a separate mode. Both regions are part of the same arena trip.