It is in Northport.

And 8 down from the surface once you are there.

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

• A rope. You drop in through a sewer grate, and a rope is how you climb back out.
• Something for demon, warlock and giant spider — they live down there.

The chest is 8 floors under the surface. Going down over it, this is what each floor uses:

1. Ground: down through stairs.
2. 1 down: down through a ladder.
3. 2 down: down through a ladder.
4. 3 down: down through a sewer grate.
5. 4 down: down through a ladder.
6. 5 down: down through a ladder.
7. 6 down: down through a ladder.
8. 7 down: down through stairs.

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

• 2 — a ladder, 1 down
• → — the treasure lies this way

• 3 — a ladder, 2 down
• → — the treasure lies this way

• 4 — a sewer grate, 3 down
• → — the treasure lies this way

• 5 — a ladder, 4 down
• → — the treasure lies this way

• 6 — a ladder, 5 down
• → — the treasure lies this way

• 7 — a ladder, 6 down
• → — the treasure lies this way

• 8 — stairs, 7 down
• → — the treasure lies this way

• 1-2 — the chests

There are 2 chests here under 2 quest numbers, so you can take them all.