It is in Havoc.

And 1 down from the surface once you are there.

• 1 — Havoc, as the map itself names it
• 2 — the ground above the treasure

• Something for dragon lord, giant spider and dragon — they live down there.

The chest is 1 floor under the surface. Going down over it, this is what each floor uses:

1. Ground: down through a ladder.

• 1 — the way in: a ladder, ground
• → — the treasure lies this way

• 1 — the chest
• 2 — Plains of Havoc (1)

The strongest 14 of 30 kinds whose nests reach this place.

One chest, one reward.