Martian Saucer

There is nothing to summon. It arrives on its own once Martian Madness is roughly a third cleared, and it keeps arriving through the rest of the invasion. It flies, it ignores terrain, and it will come through your arena walls, so a bunker does not keep it out. Each one you kill pushes the event bar along by a useful chunk, so they are worth chasing rather than running from.

It cycles three attacks in a fixed order, drifting a little closer to you between each one. Watch it twice and you always know what is next.

• The laser volley fires at the spot you were standing when the attack began. It punishes holding still and nothing else, so keep drifting and almost all of it misses.
• The missile salvo homes, but each rocket detonates on the first thing it touches. Run and let them bury themselves in the ground behind you and the entire volley is wasted.
• The deathray is the one that kills people. It slides into position over your head, fires a beam straight down, then travels for several seconds in whatever direction you were already moving.

That is the whole answer to it. Altitude is immunity, so if you can get above the saucer before the attack starts you are simply out of the fight for its duration. Wings are enough with a little warning, and anything that teleports, a Rod of Discord or a Hook of Dissonance, gets you clear instantly. If you are stuck below it, pick a direction and keep going, because reversing walks you back under the beam it is dragging behind you.

Do not try to hide under the ground. The beam looks like it stops at solid tiles, but it passes through them and finds you on the other side, exactly like the one the final boss uses.

The four weapon mounts have to be destroyed individually, and each one that goes removes its attack from the rotation. What replaces it is worse in a different way. The broken section starts shedding sparking debris that falls, lands on solid ground and sits there hurting anything that touches it. The longer the fight runs, the more of your floor becomes unusable, so an arena where you are forced to land occasionally gets steadily more dangerous. Fight it somewhere you can stay airborne.

In Classic the saucer dies when the last mount breaks. In Expert and Master it does not. The shell splits open to expose a core, it shakes violently for a few seconds, and then it comes back at you with nothing but deathrays. In that state it repositions to one side of you, sweeps across while firing, then does the same from the other side, over and over, with debris pouring from all four broken mounts the whole time. Those beams pass through blocks and hit far harder than the first phase version.

The shudder between phases is free distance. Use it to get as far away as you can, and above it if possible, before the sweeps start. With a dash the sweeps are dodgeable outright on decent timing. Without one, matching its direction of travel is the fallback.

• Anything that counts nearby enemies reads a single saucer as six separate things, since every mount, the core and the frame all register on their own.
• If the phase change interrupts a deathray, the beam freezes in place until the transition finishes.
• It is one of only three enemies with a minion weapon modeled on it, the Xeno Staff, alongside the Twins and Duke Fishron.