It is in Rookgaard, about 29 steps north-west of the spot the map marks with that name.

And 1 down from the surface once you are there.

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

The people you need are in Rookgaard, which also lists the boats that get you there and the words to say to the captain.

• 1 — the temple of Rookgaard, where you land and where you come back if you die

• Key 4600: a locked door bars the way, and that is the number of the key that opens it.
• Something for rotworm, skeleton and orc — they live down there.

• In Rookgaard: Tom

• 1 — Tom, in Rookgaard

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 — Rookgaard Rat Bridge ON (1)
• 3 — Rookgaard Rat Bridge ON (2)
• 4 — Rookgaard Academy Entrance ON
• → — the white arrow points to the side you come in from, towards Rookgaard

The strongest 14 of 15 kinds whose nests reach this place.

One chest, one reward.