Spelunky is © 2008, 2009 Derek Yu and Mossmouth, LLC, and is used under the [Spelunky User License v1.1b](https://spelunky.ai/LICENSE.txt). spelunky.ai is an unofficial fan project, not affiliated with or endorsed by Mossmouth. The game and its assets may not be sold. Music by George Buzinkai and Jonathan Perry; sound effects made in SFXR. From Spelunky Classic 1.1, © 2008, 2009 Derek Yu and Mossmouth, LLC. # Alien Boss From the spelunky.ai wiki: . Verified against the spelunky.ai port [v0.1.10](https://github.com/851-labs/spelunky/releases/tag/v0.1.10) on 27 October 2026. *For the small aliens that parachute from UFOs, see [Alien](https://spelunky.ai/wiki/alien).* The Alien Boss is a monster of the Ice Caves' mothership in Spelunky Classic that sits still and sends psychic waves at the player, each taking 1 heart. ![A big green alien with a bulging head, one eye and short tentacles](https://spelunky.ai/wiki/media/17b72a4951674638/sprites/sAlienBoss/anim%404x.png) | Alien Boss | | | ---------- | ---------------------------------------------------- | | Health | 10 hit points[^1] | | Damage | 1 heart per psychic wave, 1 heart by touch | | Behaviour | Sits still and sends psychic waves at the player[^2] | | Object | `oAlienBoss` | | Found in | The Ice Caves, Mothership | | Drops | Big Emerald, Big Sapphire, Big Ruby | The Alien Boss sits in the last room of the mothership, the alien craft some levels of the Ice Caves hold. It never moves; while the player is near, it sends a psychic wave that drifts after him and knocks him down. It has 10 hit points, and, unlike most monsters, the Whip hurts it on every step it touches it, so it doesn't last long against one. When it dies, it leaves 4 big gems and brings down the craft's barriers. ## Behaviour The Alien Boss doesn't move on its own: it only falls, if nothing is under it[^3]. **Clip: Alien Boss psychic wave.** The Alien Boss sends a psychic wave that drifts toward the player and knocks him down, taking a heart. About three seconds later it sends another. ([video](https://spelunky.ai/wiki/media/17b72a4951674638/clips/alien-boss/psychic/clip.mp4)) When the player is within 96 pixels of it, and isn't dead, stunned or invincible, it sends a psychic wave from its middle, with a sound and six sparks drawn in toward it, then waits 100 steps before it can send another, so its waves come 101 steps (about 3.4 seconds) apart at the soonest[^2][^4]. It starts with that wait too, so the first wave comes 101 steps after it's made at the earliest[^5]. The wave drifts toward the player at 2 pixels per step (60 per second), turning to follow him, until its animation ends, about 2.3 seconds later[^6][^7]. It passes through walls. It hurts any other monster it touches, but not an Alien Boss, for 3 hit points[^8]. The clip shows the Alien Boss sending a wave at the player, who loses a heart, and another about three seconds later. The Alien Boss only acts while it's on screen or just off it[^9]. ## Damage | Way | Damage | | | ---------------------------------- | --------------------------------------------------------------------------------------------------------------------- | ----- | | A psychic wave | 1 heart; knocks the player back and stuns him for 40 steps, without making him invincible; nothing while he's stunned | [^10] | | Touching it, without landing on it | 1 heart, and he's knocked away and invincible for 30 steps (1 second); nothing once it's dead | [^11] | ## Defeating **Clip: Alien Boss whipped.** The player walks into the Alien Boss, losing a heart, and whips it twice. Each crack of the whip hurts it for every step it touches it, and the second kills it; it leaves four big gems. ([video](https://spelunky.ai/wiki/media/17b72a4951674638/clips/alien-boss/whip/clip.mp4)) The Alien Boss isn't stunned by hits, and the Whip and the Machete hurt it through the code most monsters share, which has no pause between hits: they take their damage on every step they touch it[^12]. The clip shows the player whipping it: each crack took 7 hit points, and the second killed it[^13]. | Way | Damage | | | ------------------------------------------------------------------ | -------------------------------------------------------------------------- | ----- | | Whip | 1 hit point each step the whip touches it (7 a crack in play) | [^12] | | Machete | 2 hit points each step the slash touches it | [^12] | | Stomp (landing on it) | 1, plus 1 for every 16 steps of falling; three times that with Spike Shoes | [^14] | | A thrown item moving faster than 2 pixels per step, such as a Rock | 1; nothing more while it flinches | [^15] | | A stunned monster thrown into it | 1; nothing more while it flinches | [^16] | | A Shotgun or Pistol bullet | 4 hit points | [^17] | | A Bomb's explosion | 30 hit points: it kills it | [^18] | | Ending up inside solid ground | Kills it | [^19] | Its step doesn't run the one most monsters share, so Spikes, Lava, Spear Traps and water don't affect it[^20]. **Clip: Alien Boss bombed.** The player drops a bomb beside the Alien Boss and runs out of its reach before it can send a wave. The explosion kills it, and it leaves four big gems. ([video](https://spelunky.ai/wiki/media/17b72a4951674638/clips/alien-boss/bomb/clip.mp4)) When its hit points run out, the Alien Boss dies where it is and flings out 4 big gems, each a Big Emerald, Big Sapphire or Big Ruby at random[^21]. When its dying animation ends, every barrier emitter in the level is destroyed, and the barriers with them[^22][^23]. Its body stays, and can't be picked up[^24]. The clip shows the player dropping a Bomb beside it and running out of its range before it can send a wave; the explosion kills it. An Alien Boss killed counts toward the player's kills, and the screen between levels draws its icon[^25][^26]. ## Locations Level generation makes the Alien Boss only in the mothership. An Ice Caves level after the Moai's has a 1 in 10 chance of holding the alien craft: a row of rooms from a random one to the level's right edge[^27][^28][^29]. The last of them, at the edge, is the only room with the Alien Boss, beside a barrier emitter and a free Jetpack set in a block[^30][^31][^32]. In custom levels, it's the level editor's tile `E`[^33]. ## Tips - It only sends a wave while the player is within 96 pixels, so staying further away is safe, and walls don't stop its waves. - A stunned or invincible player draws no wave, and a wave can't hit a stunned one. - Its waves are 101 steps apart at the soonest: right after one is the time to get close. - The Whip does more against it than against most monsters: two cracks are enough. ## Trivia - Its step sets the same sprite whichever way it faces, in two lines[^34]. ## FAQ ### How much damage does the Alien Boss do in Spelunky Classic? 1 heart per psychic wave, which also knocks the player down, stunned, for 40 steps. Touching the Alien Boss costs 1 heart too, unless it's dead. ### How do you kill the Alien Boss in Spelunky Classic? It has 10 hit points. A Bomb kills it outright, and the Whip hurts it for every step it touches it, so two cracks kill it. A stomp, a thrown item or a bullet takes less. ### How often does the Alien Boss attack in Spelunky Classic? At most once every 101 steps (about 3.4 seconds), and only while the player is within 96 pixels of it and neither stunned nor invincible. ### What does the Alien Boss drop in Spelunky Classic? 4 big gems, each a Big Emerald, Big Sapphire or Big Ruby at random. Its death also brings down the mothership's barriers. ### Where is the Alien Boss in Spelunky Classic? In the mothership, the alien craft some Ice Caves levels have: it sits in the craft's last room. ## See also - **Damaged by:** Whip, Machete, Stomping[^14], Throwing[^15], Shotgun[^17], Pistol[^17], Bomb[^18] - **Related:** [UFO](https://spelunky.ai/wiki/ufo) ## References [^1]: `objects/oAlienBoss/create.gml:10` [^2]: `objects/oAlienBoss/step.gml:63-75` [^3]: `objects/oAlienBoss/step.gml:43-58` [^4]: `objects/oPsychicCreate/create.gml:7` [^5]: `objects/oAlienBoss/create.gml:29` [^6]: `objects/oPsychicWave/step.gml:1-3` [^7]: `objects/oPsychicWave/other_animation_end.gml:1` [^8]: `objects/oPsychicWave/collision_oEnemy.gml:1-7` [^9]: `objects/oAlienBoss/step.gml:1-3` [^10]: `objects/oPlayer1/step.gml:1594-1612` [^11]: `objects/oAlienBoss/collision_oCharacter.gml:11-28` [^12]: `objects/oEnemy/collision_oWhip.gml:1-8` [^13]: Clip alien-boss/whip [^14]: `objects/oAlienBoss/collision_oCharacter.gml:1-10` [^15]: `objects/oItem/step.gml:320-330` [^16]: `objects/oEnemy/step.gml:232-242` [^17]: `objects/oBullet/collision_oEnemy.gml:16` [^18]: `objects/oExplosion/collision_oEnemy.gml:12-19` [^19]: `objects/oAlienBoss/step.gml:4-7` [^20]: `objects/oEnemy/step.gml:34-128` [^21]: `objects/oAlienBoss/step.gml:9-25` [^22]: `objects/oAlienBoss/other_animation_end.gml:1-5` [^23]: `objects/oBarrierEmitter/destroy.gml:8-11` [^24]: `objects/oAlienBoss/create.gml:17` [^25]: `objects/oAlienBoss/step.gml:26-31` [^26]: `objects/oTransition/alarm_0.gml:215-219` [^27]: `scripts/scrLevelGen.gml:222-233` [^28]: `scripts/scrClearGlobals.gml:59` [^29]: Quirk 1 (docs/quirks.md) [^30]: `scripts/scrRoomGen3.gml:175-180` [^31]: `scripts/scrRoomGen3.gml:461-464` [^32]: `scripts/scrRoomGen3.gml:472-478` [^33]: `scripts/scrCreateTileObj.gml:213-216` [^34]: `objects/oAlienBoss/step.gml:79-86` ### Source code - `objects/oAlienBoss/create.gml` - `objects/oAlienBoss/step.gml` - `objects/oAlienBoss/collision_oCharacter.gml` - `objects/oAlienBoss/other_animation_end.gml` - `objects/oPsychicWave/step.gml` - `objects/oPsychicWave/collision_oEnemy.gml` - `objects/oPsychicCreate/create.gml` - `objects/oEnemy/create.gml` - `objects/oEnemy/collision_oWhip.gml` - `objects/oPlayer1/step.gml` - `scripts/scrLevelGen.gml` - `scripts/scrRoomGen3.gml`