Echo in the Lightless Deep is a deep-sea survivor roguelite. You guide a small light core down from the surface, through five zones of a sunless ocean, to the seafloor 1,050 meters below. Down here, your glow is one of the only lights there is.

Brightness is the heart of the game. It sets how far you can see, how far your symbionts can strike, and how far away a monster notices you. Collect motes and pick light-side mutations and the light grows, and so does everything that comes to meet it. Go dim and you're safer. Where to hold that trade is what every dive is made of.

Combat runs itself. Symbionts orbit the core and tear into whatever comes close, and rare ones you cross in the dark — a lantern jellyfish, a blind cleaner shrimp — will join you if you drift near, each with its own job: lighting the way, soaking hits, straining motes from the water. They have loyalty meters; run them down and they leave for a while. What you actually do is steer, dodge, and time three skills:

Lights-Out: dim to near-black. Far fewer monsters appear, your damage halves, dark energy builds faster, and the first hit on anything that hasn't spotted you deals 2.5× damage. Also the best way to shake a tail.

Echo Pulse: spend 40% of your dark energy to send out a sonar ring. Everything it touches is marked for 4 seconds and takes triple damage.

Light Devourer: needs a full bar of dark energy. For 12 seconds your orbiting symbionts deal 2.5× damage and new monsters nearly stop spawning. When it ends, your light is permanently 15% dimmer for the rest of the run.

Level-ups offer a three-card pick from 59 mutations in three families. Light mutations keep compounding your brightness and your damage; dark mutations buy survival and vision, and make light cards rarer from then on; neutral cards stay out of the way. Twelve fusion recipes turn two mutations into an evolved one, across three build paths: Lumen Hunter, Abyss Stalker, Devourer. The end of one of those paths hides the true ending.

The descent is automatic; your problem is staying alive through each layer. A giant holds each of the five depths: 150, 320, 500, 800, and 1,050 meters. They are earlier descenders, warped by their own obsessions into the largest predators in this sea, and each one leaves a relic behind. Depth hones the hunters too: their projectiles get faster all the way down, and near the bottom the barrage outruns you. The giants have tempers, too: drop a giant's health past a threshold and it escalates into a second, then a third phase — new attacks, a rage tempo, an entrance worth surviving.

Six waters, six kinds of trouble: darkness that burns, seabeds laced with mines, currents that read your position aloud to the hunters, lights that are bait. Every run reshuffles species, forms and behaviors from its seed, so no two descents meet the same fauna.

Once per dive, a whale falls. Motes and monsters converge on the carcass, and whether to join that feast is yours to weigh.

Wherever you die, an extinguished core stays on the seafloor; pass it on a later run and it shows your depth, your cause of death, and whether your light was on. Thirty-nine whispers drift through the five zones, sounding more and more like one voice. Gather all eight origin fragments and the last one hands you a sentence that explains what your light actually is; the final choice reads differently after that.

There is no victory screen at the bottom. You can relight and rise back to the surface, or stay dark and remain part of the abyss. A third path sits at the end of one of the build routes.

Restarting after death is instant. Single-player, playable offline, one-time purchase, no ads or microtransactions.

Combat

• One light core, two stances: lit buys vision and reach, dim buys safety — every dive is a negotiation with that trade

• Orbital symbionts fight on their own: two orbit the core from the start, tearing into anything close; mutations add more and sharpen them

• Three active skills — Lights-Out, Echo Pulse, Light Devourer — all fully remappable

• Threats beyond your light render as full silhouettes: segmentation, spines and heading stay readable

Builds

• 59 mutations in three families: light compounds your power, dark trades light for survival, neutral stays out of the way

• 12 fusion recipes that merge two mutations into an evolved one

• 3 build paths — Lumen Hunter, Abyss Stalker, Devourer — and one of them ends in the true third ending

World

• A 1,050 m descent through 5 depth zones and 6 waters, with 36+ pack behavior variants

• 5 giants at 150 / 320 / 500 / 800 / 1,050 m — multi-phase fights, each leaving an obsession relic

• Hunters get faster with depth; near the bottom, the barrage outruns you

• Once per dive, a whale falls: motes and monsters converge — join the feast or slip past

• 3 rare symbionts found in the wild: lantern jelly, cleaner shrimp, anglerfish fry — loyal, until you spend their loyalty down

• Procedural generation: every run reshuffles species, forms and behaviors from its seed

• The Abyss Map: 72 tiles assembled across runs — find the hidden shapes, uncover the secrets

The longer haul

• 3 modes: Quick (500 m) / Full (1,050 m) / Abyss (endless)

• 100 achievements · 4 Depth Trials · Weekly Abyss — one fixed seed, every player, every week

• Steam Cloud saves · global leaderboards (deepest dive / best single-run hunt)

• Offline single-player · one-time purchase · no IAP · no ads

Controls & accessibility

• Full key remapping with conflict detection and one-click reset

• Reduced screen shake / reduced flash toggles

• One-click fullscreen/window toggle

• Colorblind-friendly mutation glyphs: ☀ / ☾ / ◈ / ★

• Gamepad: left stick to steer, face buttons for skills, a virtual cursor that reaches every screen, rumble and in-game pad settings