Boss Strategy & Formations
Boss fights aren't luck — both the timing and the lane are known in advance. This page covers the boss cycle, the advance warning, how targeting actually works per unit, and how to build a formation around that, all based directly on the game's own logic.
A boss always comes every 5 days
A boss appears on day 5, 10, 15, 20, and so on — every multiple of 5. A standard 20-day run has 4 boss fights total, and Endless mode keeps the same 5-day rhythm past day 20. It's not a surprise ambush; it's a fixed beat you can prepare for.
The lane is warned during that same day
During the day phase of the boss's own day, the lane it will descend on lights up with a flashing red band ("↑BOSS↑"). It appears while you can still move tiles, so you get a window to rearrange your formation around that lane after seeing the warning.
Every unit targets differently — this matters a lot for bosses
The single most important thing for formation-building is that units don't all reach the same area. Whether a unit can hit an adjacent lane varies a great deal by unit.
| Targeting type | Units | Hits adjacent lanes? | Shape |
|---|---|---|---|
| Omnidirectional | Archer, Heavy Guard, Mage, etc. | Yes (if within range) | Circle |
| Column (own lane only) | Sniper | No — only its own lane | Straight line down the column |
| Row (own row) | Gunner | Yes (crosses lanes at the same height) | Straight line across the row |
| Spear's fixed shape | Spear | Reaches 1 diagonal tile only | 2 tiles up/down + 1 diagonal |
The critical detail: a Sniper can only hit enemies in its own lane. If you want a Sniper's hit to land on the boss, it has to be placed directly in the boss's own lane. From an adjacent lane, its attacks never reach the boss at all.
The standard formation: block and support
The most reliable approach blocks the boss's lane and piles damage on it while it's stuck.
- Place a Heavy Guard directly in the boss's lane — it's the only unit that can hold it in place, so it's the anchor of this formation
- Put a Medic adjacent to that Heavy Guard for continuous healing and a damage boost
- If you want a Sniper in the mix, line it up in the same lane as the Heavy Guard (since it can only hit its own lane) — stacked vertically, its piercing hit keeps landing on the held boss
- As long as the block holds, nearby Mages (area) and Gunners (splash at the same height) can also join in from adjacent lanes
An alternative: unblocked focus fire
Instead of blocking, you can let the boss walk close to the castle unimpeded and focus-fire it from adjacent lanes with units whose range reaches across. Bosses move slowly, so surrounding it with units that reach multiple lanes can keep the damage flowing without a block at all.
This works with omnidirectional units (Archer, Mage) and Gunners (splash, at the same height). Snipers don't fit this tactic — from an adjacent lane their attacks never reach the boss, so unless a Sniper sits in the boss's own lane, it's wasted here.
The trade-off is straightforward: without a block, the risk of the boss reaching the castle and damaging your Ember goes up, but you're not tying up a tile in the boss's own lane, so you can bring more units to bear on it at once. Useful in the early-to-mid bosses while Ember is plentiful, or before your Heavy Guard is trained up enough to hold reliably.
Ember Shards from day 20 onward (Endless)
Once you push past a boss into Endless mode, Ember Shard rewards accelerate with depth starting on day 21.
| Depth reached | Approx. shards | Note |
|---|---|---|
| Day 20 | 36 | Standard run clear (unchanged) |
| Day 25 | 144 | |
| Day 27 | 243 | Roughly the median depth for a typical roster |
| Day 29 | 373 | Roughly the upper range for a typical roster |
| Day 30 | 449 | |
| Day 35 | 941 | Often cited as the difficulty wall |
A typical, reasonably-built roster tends to run out of steam around day 27-29 in practice. See Endless Mode & Ember Shards for the full breakdown of the reward curve.
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Unit Roles Explained · Endless Mode & Ember Shards · Dusk Legion