“Undermine delves” are the two delves added with The War Within patch 11.1 Undermine(d): Sidestreet Sluice, inside the goblin city of Undermine itself, and Excavation Site 9 out in the Ringing Deeps. Both run on the familiar 1–11 tier ladder with Brann Bronzebeard at your side. They were Season 2’s stage for Overcharged modifiers and The Underpin solo boss, and they are still open today as War Within content alongside Midnight’s current-season delves.
Quick facts
| Delve | Zone | Notes |
| Sidestreet Sluice | Undermine (Isle of Kezan) | The only delve physically inside the goblin city; waterway and pipeworks theme |
| Excavation Site 9 | Ringing Deeps | Added in the same patch; goblin dig site rather than a city setting |
| Tiers | 1–11 | Same ladder as every other delve; Bountiful versions need a Restored Coffer Key for the bonus chest |
| Seasonal boss | The Underpin | Season 2’s solo challenge, the successor to Zekvir, with a harder “??” difficulty |
| Status in September 2026 | Previous expansion | Gear from them does not compete with Midnight-season item levels |
- Access starts with the Undermine(d) campaign, which kicks off in Dornogal and takes you to Kezan; once the city is open, Sidestreet Sluice shows up on the delve map like any other.
- Both delves accept the standard Brann levels and delve-tier unlocks you already have on the account; nothing separate to grind.
- Overcharged runs added hazard mechanics for a bonus payout — worth doing once for the achievement, not something you need to farm now.
Where exactly is the Sidestreet Sluice delve?
It sits below street level in Undermine, reached through the city’s drainage and pipe network rather than an open-world cave mouth. If you have not unlocked Undermine yet, the map pin will not help you: finish the intro leg of the 11.1 campaign first, then the entrance appears on the zone map with the usual delve marker.
Excavation Site 9 is the one people mix it up with. It belongs to the same patch and shares the goblin theme, but it lives in the Ringing Deeps, so if a guide says “Undermine delves” it usually means both together.
Are Undermine delves still worth running in Midnight?
For gear, no. Their reward track is War Within Season 2 and Midnight’s ladder sits well above it, so a Tier 11 Sluice clear will not move your item level today. Midnight delves, their Ritual Site events, and the Nullaeus encounter are the current progression path.
For completion, yes. The delve achievements for the two locations, the Underpin kills, and the story beats around the Cartels are all still there. Some seasonal cosmetics were tied to Season 2 and may no longer drop, so check the achievement panel before you commit an evening to chasing a specific reward.
What was The Underpin encounter?
The Underpin was Season 2’s solo delve boss, built the same way Zekvir was in Season 1: an optional fight with a normal “?” difficulty and a punishing “??” version aimed at players who want a real solo test. Expect heavy hits, a tight enrage and mechanics you cannot ignore. Cheat-death cooldowns, potions and a fully upgraded Brann matter more here than in a regular tier run.
How do Undermine delves differ from Midnight delves?
Structure is identical: pick a tier, clear objectives, loot the chest, open the Bountiful bonus with a Restored Coffer Key. What changed in Midnight is the reward ceiling, the companion progression, and the seasonal extras — Ritual Sites events and the Nullaeus challenge replace Overcharged runs and The Underpin as the “extra credit” layer. If you are gearing a fresh character today, spend your keys on Midnight delves and treat the Undermine pair as a weekend side trip.
If you would rather have a vetted human player alongside you for the harder tiers or the solo bosses, PewPewShop offers delve coaching and play-together help: a Delves Boost starts from EUR 17, Tier 11 clears from EUR 44, and the Midnight Nullaeus encounter from EUR 38.99 — no bots, no shortcuts, just an experienced player showing you the route.