UFOs generally patrol a horizontal space, only turning when they reach a wall. They will passively float around until a potential target appears under them. This target can be a Spelunker, Hired Hand, Olmite, or Lamassu.
Once a target is under them, it attacks by firing a slow-moving bolt of plasma straight down, dealing 1 damage to what it hits. This bolt will be destroy a single tile if it touches the ceiling and does not hit an enemy.
- Oddly, this projectile grants invincibility frames to every single entity it hits, regardless of whether it is a player or not.
- If a UFO initially fires a projectile in response to a player or Hired Hand, they will be blamed if it destroys the block of an Altar or Shop, or if it triggers a trap such as the Golden Idol Boulder trap in The Ice Caves.
Although this projectile is for the most part innocuous, the true danger of a UFO is when it is damaged via any means. Doing so will cause the Alien pilot inside to lose complete control of the ship, cause it to move slightly upward, and send the flying saucer crashing down, exploding once hitting a floor or ceiling, but never from hitting a wall.
If the ship falls for enough time, the Alien inside will eject the ship and attempt to land safely using a Parachute. If the alien does not successfully eject from the UFO before detonation, there is a small chance of the Parachute item itself dropping.
Freezing a ship and destroying it will not leave an explosion behind, and is a safe way of removing UFOs from a situation.
- A player should be wary of UFOs, especially in Neo Babylon, where Spark Traps and other hazards will send it flying in chaotic, sometimes unpredictable directions and lead to an explosive death.
- If a player steps on the left side of the UFO, it will fall to the right, while stepping on the right side will cause it to fall on the left. This can move the UFO into a much more preferable direction to where it will not hurt the player.
- UFOs will attempt to attack enemies through floors, allowing a player under it to carve holes through the ceiling using its projectiles in order to create new passageways.
- UFOs attack Olmites, including those wearing a helmet, in which case reflecting the UFO's projectile back at and causing it to crash; one should be wary of such a situation.
- UFOs in Olmec's Lair will instantly explode when summoned by Olmec when he is too close to a wall, making for an easy way to dispatch of them.