Slayer and I faced the Lunar today. We have some stuff to tell you.
Part 1: Cultists
Neutral mobs outside the dungeon, respawn every day after Golem dies. Not too hard; when they die, though, the Lunatic Cultist is summoned. He teleports, makes duplicates and has a variety of devastating attacks. Use stuff like the Flairon.
When he dies, you are given a brief grace period before the celestial event begins...
Part 2: Celestial
During this, your world is divided into four parts, with a small neutral zone in-between them. Your spawn is clear. Each segment is different; one is Solar, one Vortex, one Nebula and one Stardust. These are melee, ranged, magic and summoner respectively. You will have to fight a certain number of monsters in each zone before the pillars' defenses go down, and they can be defeated.
Melee-themed zone: lots of landbound monsters to fight. To keep you from just kiting (because they are very powerful) there's an unkillable, very fast worm type thing called the Crawlipede. The thing's a jerk, and it's very likely to murder you... if you leave the ground. Stay there. It's safe; it hates the ground. Be sure to collect the fragments when you're done!
- Selenion (sp.?)
- Drakonian Rider (sp. ?)
You'll know you're here when it starts going dark green, aliens start spawning, and lightning streaks the sky. Riddled with fast, powerful ranged monsters such as the Alien Queen, the Vortex is very difficult for slower players who can't dodge shotgun blasts. The aliens, they've learned to speak American.
- Alien Queen
Probably the hardest single zone, it's full of highly dangerous monsters and is bright purple. You'll be taking lots of damage here and you may not even be safe in the neutral zones, because they can teleport. There's also a lot of them, and they can latch onto you (hello, headcrabs) and even blind you.
- Nebula Headcrab
- Brain Suckler
- Evolution Beast
This one has a lot of enemies, 'cause they divide and conquer you. True to its nature, the summoner zone can summon lots of ickies to fight you, but they're not too dangerous. It's blue and sparkly!
- Stardust Cell
Part 3: Utter Wreckage
Once you've defeated all the zones (a time-consuming task) you'll be given a brief period of time before the Moon Lord spawns. The dude looks like Cthulhu and seems to be modeled after Necromitron, from TCF. Kill his hands first; each has 25000 HP and is a problem. You'll be locked in place the entire fight by a debuff similar to The Tongue, so be careful. He'll occasionally sweep you with a laser; that's when his eye, the vulnerable part, opens. Once the hands are dead, he'll start attacking you with eyeballs. Kill him anyway!
...we haven't gotten past him yet, so we don't know what's beyond him. More to come.