Sunken Ruins — Map Guide
Sunken Ruins is Mission 06 — a half-drowned ancient city where flooded water channels eliminate most of the positioning slots you're used to having, every enemy is undead and immune to bleed, and the Hollow King boss summons skeleton reinforcements that your towers must kill simultaneously. The map forces you to fight smarter with fewer options. This guide covers how.
Map Overview & Terrain
Sunken Ruins depicts a once-grand ancient city that has partially subsided into a waterlogged marsh. The ruins' stone streets are still visible, but wide water channels cut diagonally across what would otherwise be open terrain — blocking tower placement in entire zones and forcing enemy movement through only two narrow raised causeways that cut between the flooded sections.
The terrain effect is severe: roughly 40% of the map's ground tiles are water, impassable to both enemies and towers. This forces enemy movement into tight raised causeways that create natural chokepoints. It also means your tower options are dramatically restricted — many positions that would be ideal on a dry map are simply flooded here.
All enemies on Sunken Ruins are undead. This has one critical mechanical implication: undead enemies are immune to bleed. Any item or ability that applies bleed — including the Ivy Bow's secondary bleed proc and several other Rare-tier items — deals zero damage to undead. Do not carry a bleed-heavy loadout to this map.
Map Layout Diagram
Two enemy spawn points feed into two raised causeways separated by a major water channel. The causeways converge at a ruined bridge section before your base. Chokepoints A and B are at the narrowest sections of each causeway.
Best Chokepoint Positions
The water channels create the chokepoints for you — the causeways are narrow by design, and every optimal tower position is dictated by where the causeway is narrowest. There is less strategic decision-making about chokepoint placement here; the map forces the layout.
The left causeway is bordered on both sides by water channels, creating a single-tile-wide kill corridor. Your main Defender belongs here. The water on both sides means there are no lateral placement options — the Healer cannot go beside the Defender, it must go directly behind it. This is actually beneficial: a behind-position Healer takes no incoming enemy damage and heals the Defender from a protected rear angle. Skeleton Archers (Wave 3+) fire from range — position the Healer far enough back that Skeleton Archer shots can't reach it at their firing range.
The right causeway mirrors the left in structure but carries faster undead enemies — Drowned Runners (Wave 1+) and later Drowned Giants (Waves 5–6). A Defender at Chokepoint B stops Drowned Giants effectively. The challenge is tower supply: if you've committed your main party to Chokepoint A, you need a solo Archer or second Defender here. Drowned Giants have high HP and hit hard — an isolated Archer cannot sustain them alone in Waves 5–6. A second Defender is the recommended solution if your item loadout supports it.
Wave-by-Wave Breakdown
Six waves of undead enemies before the Hollow King. Waves 1–2 are manageable skeleton and drowned unit varieties. Wave 3 introduces Skeleton Archers who fire from range before reaching your chokepoint. Waves 5–6 bring Drowned Giants — the highest-HP non-boss enemies in the game so far.
| Wave | Enemies | New Threat | Priority Action | Danger |
|---|---|---|---|---|
| 1 | Skeleton Warriors (L) + Drowned Runners (R) · Both causeways · Bleed immune | Bleed immunity on all enemies | Verify no bleed-based items are equipped before this wave. Skeleton Warriors have moderate HP and standard attack. Drowned Runners are fast but fragile. Establish both chokepoints and confirm Healer is behind Defender (not beside it) given the narrow causeway. | Low |
| 2 | Skeleton Warriors + Rotting Ghouls · Left causeway heavier · First tanky undead | Rotting Ghouls (high HP, slow, physical resistance) | Rotting Ghouls resist physical damage. Magic or fire items handle them efficiently. Their slow speed means they queue up at Chokepoint A — sustained DPS clears them; just ensure Archer has a magic-damage item active. | Low |
| 3 | Skeleton Archers (both causeways) + Rotting Ghouls (L) · Ranged units first appear | Skeleton Archers (fire from range before reaching chokepoint) | Skeleton Archers fire at your Defender from 4 tiles away. They deal damage before they even arrive at the chokepoint. Move your Healer two tiles further back from its Wave 2 position — Skeleton Archer shots can reach the original Healer position. Your Archer must prioritise Skeleton Archers over melee units. | Medium |
| 4 | Skeleton Archers + Elite Skeleton Warriors + Ghoul Berserkers · Dense · Both causeways | Ghoul Berserkers (fast, high damage, no HP resistance) | Ghoul Berserkers have low HP but extremely high attack speed — they burst your Defender faster than any previous enemy. They die quickly to Archer fire but if they reach the Defender before being shot, they deal significant burst. Ensure Archer #1 fires on Berserkers before melee units when both are present in the same wave. | Medium |
| 5 | Drowned Giants (R) + Skeleton Archer squads (L) + Rotting Ghouls · Very high HP | Drowned Giants (enormous HP, slow, physical and magic resistance) | Drowned Giants appear on the right causeway exclusively. They have the highest HP of any regular enemy so far — higher than Root Elementals. A single Archer cannot sustain kill speed against them. If you have a second Defender at Chokepoint B, it holds them; if not, DPS races become critical. Fire damage is their only non-reduced damage type — ensure Archer #2 has a fire item if at all possible. | High |
| 6 | Drowned Giants + Elite Skeleton Archers + Ghoul Berserkers · All types · Maximum density | Elite Skeleton Archers (longer range, higher damage) | Elite Skeleton Archers fire from 6 tiles — further than regular variant. Reposition Healer to 4 tiles behind Defender before this wave. Elite Archer shots at 6-tile range can hit the regular Wave-3 Healer position. After clearing: full heal, Cauldron, Hollow King pre-pull setup. | Pre-Boss |
Key Mechanics: Undead Immunities & Water Channels
Bleed immunity (all undead)
Bleed is a damage-over-time effect applied by several item abilities — most commonly Ivy Bow's secondary proc and the Serrated Blade item. Against undead, bleed deals zero damage. The animation and screen indicator still appear, which can mislead players into thinking bleed is applying normally. It is not. Check your DPS numbers: if they're lower than expected on this map, bleed is the likely culprit.
Items that use bleed exclusively as their primary effect should be removed from loadout entirely before entering Sunken Ruins. Items with bleed as a secondary effect (alongside a primary damage type like magic or fire) are worth keeping — the primary damage still applies, you just lose the secondary bleed bonus.
Water channels and positioning constraints
The water channels that fill 40% of the map create forced chokepoints, but they also restrict repositioning. If your Defender is displaced during combat (pushed back by an enemy ability, for example), there may be no tile to step back to except directly down the causeway — back toward your base. Plan for this: a Defender pushed back two tiles from Chokepoint A is now four tiles from the enemies queuing at the chokepoint, reducing its blocking effectiveness entirely. Watch for enemy push abilities and pre-position with extra space.
Skeleton Archer firing range mechanic
Skeleton Archers fire at your Defender from a fixed range, beginning their attack cycle before they arrive at the chokepoint. This is different from every enemy type encountered on previous maps — most enemies only deal damage when at melee range. The result: your Defender starts taking damage earlier in the wave than the chokepoint position suggests. Healer sustain needs to be active from the moment Skeleton Archers appear on-screen, not just when they reach the chokepoint.
Recommended Tower Setup
The causeway layout forces column formations on both paths. There are no lateral positions. This setup handles all six waves and positions correctly for the Hollow King fight.
Item Priorities for This Map
Bleed is useless here. Fire damage is the single most effective damage type against Drowned Giants. Magic damage handles Rotting Ghouls. Physical damage is partially resisted by multiple enemy types.
Priority items for this map
Pyromancer's Quiver on your primary Archer adds fire damage to every shot. Drowned Giants have no fire resistance, making this the most efficient damage item for the map's tankiest enemies. Against Waves 5–6 with multiple Drowned Giants on the right causeway, the fire damage increase is the difference between killing them before they stack and having a permanent queue that never clears.
Holy Flame is a Rare-tier item with a passive undead-damage bonus — any attack that would normally deal X damage deals 1.35X against undead targets. Against a fully undead roster, this is a reliable DPS multiplier on every single enemy without any bleed or type-specific caveats.
Lightning Ward on your Defender provides magic resistance, which matters specifically against the Hollow King's necromantic attack type. It also provides a small counter to Skeleton Archer ranged shots during the regular waves.
Hollow King — Boss Phase
The Hollow King is a necromancer-type boss located at the deepest ruined hall of the map, past the bridge convergence zone. Its most distinctive ability is Skeleton Summoning — during combat, it periodically raises skeleton reinforcements from the ruined floor tiles surrounding it. These reinforcements are fully functional enemies that attack your towers while the boss is alive. Unlike the Forest Warlock's vine walls, skeletons must be actively killed.
The key strategic decision during the Hollow King fight is target priority. The boss has significant HP, but summoned skeletons can overwhelm your party if ignored. Experienced players split Archer attention: Archer #1 maintains boss DPS while Archer #2 clears skeleton adds. The Defender holds the boss; the Healer keeps the Defender alive through skeleton attack contributions.
Full phase breakdown of the Hollow King including skeleton summon timing, add-clear priority, when to switch to boss DPS, phase 2 bone wall mechanics, and phase 3 Death Shroud positioning. The guide also covers the specific undead-damage items that make the boss significantly faster to kill.
→ Read the Hollow King Boss GuideCommon Mistakes on This Map
Bringing a bleed-based loadout
The most common mistake is carrying items from Deep Forest or Bay Harbour that apply bleed — most players have Ivy Bow from Whispering Woods prep and forget that undead negate it entirely. Check every item slot before the first wave. Replace anything with bleed as its primary effect. Holy Flame or Pyromancer's Quiver in the same rarity tier deal more damage against this enemy roster than any bleed item.
Ignoring Skeleton Archers until they reach the chokepoint
Wave 3's Skeleton Archers start dealing damage from 4 tiles away. Players who wait until they arrive at the chokepoint have already taken several seconds of ranged damage to their Defender without healer response, because the Healer isn't triggered until the enemy is closer. Watch the causeway entrance for Skeleton Archers and ensure your Healer is active and the Defender starts its high-regen cycle immediately.
Not having fire damage items against Drowned Giants
Drowned Giants in Waves 5–6 resist physical and magic damage. Without fire damage, they sit at the right causeway chokepoint for a long time taking reduced damage — long enough for more Giants to stack behind them, creating a queue that eventually breaks through. Players who notice their right-path Archer barely denting Giants in Wave 5 need to make an emergency Cauldron run between waves 5 and 6 to add fire damage before the final wave.
Not killing skeleton adds during the Hollow King fight
Many first-time Hollow King attempts fail because both Archers focus the boss while skeletons pile up around the Defender and Healer. Skeletons deal cumulative damage — one skeleton hitting the Defender is manageable; six skeletons hitting it simultaneously overwhelms the Healer's output. Split Archer DPS: one on boss, one on adds. Accept that the boss fight takes longer — survival is more important than kill speed here.