Free ships granted by a random event.

Maybe... maybe if your ships were all inside your space at the time of the Peacekeepers' arrival, they may have considered you 'peaceful' and attacked anyone else who had ships outside(like those with trade routes). They must've not adapted to you having sent your ship into foreign space and still remained friendly with you.

There is no such thing as a Doom Missile in GC2. The highest end weapons are Doom Rays, Black Hole Generators and Black Hole Eruptors. The highest end defenses are Ultimate Invulnerability, Zero-Point Armor and Aereon Missile Defense. Doom Missile and Ultimate defenses sounds like you've been playing beam/shield combos too long.

A Precursor Ranger is a ship that as a random event you can find on a planet that you own. Early in the game, especially, its fairly powerful, with stats in the low double digits.

After a long session of playing with these frakking peacekeepers, I have much wisdom to impart.

1: Don't engage the peacekeepers until you have significantly surpassed the level of tech that you had when they appeared! If you didn't figure this out on your own, though, I can't really help you.

2: Use them for defense! You can't defend worlds they patrol anyway, so if a transport slips in you have no way to stop it. Just rely on their "protection" to keep your worlds safe.

3: Use them for invasion! Build fast transports (say 10+ pc/turn) to rush through their patrol and take the worlds they're near. You can have some fun wars when the enemy can't defend himself.

4: Don't overestimate them! If you assume they're everywhere and all-powerful, you may rely on their "protection" in areas they don't patrol. They seem to stick around their origin location, so if you have a planet in a contested area and don't see any peacekeepers within 10 spaces, do NOT assume you can leave it undefended!

5: MUST MUST MUST get the sensor achievement (eyes of the universe?) This single achievement is probably the main reason I'm doing so well in my game. I can keep tabs on those bastards from a very safe distance! In a normal game, this achievement is pretty cool, but when the peacekeepers hit it is a must have!

6: Don't bother with military buildup if the map has significant peacekeeper presence (unless you've surpassed their power). Just build small assault fleets and a few transports, otherwise you're spending money on maintaining a fleet that's largely unnecessary. The peacekeepers will do a good job of keeping all fleets at a minimum, so why try to be the military superpower at this stage?

7: Be alert! Autopiloted ships don't avoid peacekeepers any better than normal enemies. I have been doing a lot of going "the scenic route" with my ships to be sure they don't hit the peacekeepers. It's surely overkill, but after a few 3-billion-troop transport losses, I'm happy to lose a turn or two being cautious.

8: Lead them to enemies, not starbases! I don't know all their rules, but the peacekeepers will sometimes chase down a rogue ship in their realm and then go for another nearby ship that previously was outside their patrol area. It can be very useful for taking a world that has defenses - throw some fodder near the world, watch the peacekeepers clean it up for you. But it can be devastating as well. I was trying to run through a patrolled area, so I went toward my very decked-out military resource starbase which so far had been safe. When the peacekeepers decided to give chase, they apparently noticed this starbase for the first time.... Bye bye bonuses.

9: Get the eyes of the universe! I'm not kidding. Sensors are great, but without that you're practically blind. GET IT! I can't stress this enough.

I have had the PeaceKeeper event twice now and in one case they left me alone and in the other they took my ships apart until I reached a stage where I could go toe to toe with them then they just vanished. In the first event I was listed as a Good empire and in the second I was listed as an Evil empire...In both cases the PKs went after the evil empires but ignored the Good empires and only went after war ships of neutral empires. Maybe your alignment determines how the PKs respond in their invasion tactics.

Just bought DA, and now you guys are making me want to run back to my nice, safe GalCiv DL, with no Peacekeepers/makers/whatever and none of these 'pirates', at least not in any of my games there.

I had Mega Pirates two games ago, for the first time. When they came, I had already effectively taken an unbeatable lead against the surviving Torian, Arcean, Terran, Thalan and Krynn AI, and was armed with Black Hole Eruptors with Ultimate Invulnerability and Aereon Missile Defense as my defense options. I also had Eyes of the Universe. The Pirates had extreme Point Defense levels and Shield levels and were armed with Mass Drivers and Beam Weapons. I unified all my warships(small anti-transport interceptors, medium frigates and large battleships) into one parsec, fleeted as many as possible together into an Anti-Pirate Force, and rounded up all my utility ships into a stack under the Anti-Pirate Force for protection. I researched like wild into armor and mass drivers while my Anti-Pirate Force successfully managed to destroy 6 pirate fleets for the loss of one frigate and crippling of several others. By the time I had upgraded with Zero-Point Armor, the Pirates had backed off and concentrated against the AI races, so I went on the offensive and began slaughtering them, to the point that my surveyors could resume anomaly patrols under manual guidance. Then, while I had researched up to HD Spike Driver 4, all the Pirate Fleets vanished. Only the singleton ships remained, who soon got hunted down once my even more effective Black Hole Generator armed ships arrived. The AI races, with the exception of the Mass Driver armed Thalans, had been wiped clean of all their ships and starbases, paving the way for a constructor-spam session on my part which led to me taking over all but 1 of the galactic resources and setting up Influence Starbases that would soon conquer the galaxy(through cultural-assimilation-based conquest victory). The Mega Disease(not the Plague, mind you) event also occurred at the zenith of the Pirate Wars, but had no effect other than to delay my armor research by 2 turns.

Amazingly, the Pirates never attack Minor Races, who are able to keep their useless starbases and tons of trade routes alive through all odds. Maybe an extremely-mega Mega Event could be where the Jagged Knife appears with the Mega Pirates as their military force and declares war on everyone. Or an antithesis of this event where the Fundamentalists appear and are defended vehemently by the Peacekeepers. The first idea would have potential to conquer the galaxy, the second idea would cripple(or inhibit to an extent) all evil races in a galaxy.

BTW, is there any difference between the Pirates(who I've had in both the normal and Mega variants) and the Peacekeepers(who I still haven't seen)?

I just don't get the problem with mega events. The whole point is that they totally disrupt the game. I abhor a couple of them (particularly the one that effectively puts the game on a timer by giving seemingly-random boosts to one race every turn), but the point is to make the game totally change when they pop in. Pirates are one I haven't dealt with, but they only attack your ships, right? And if nobody in the galaxy can fight them, doesn't that mean you have time to concentrate on your infrastructure and research? If I'm not mistaken, that should be a perfect time to build up your research and get some strong anti-pirate defenses! What's the problem?

EDIT: I guess I should say that I find it odd that people who don't like the mega events get angry. If you don't like game balance going to hell via mega events, turn 'em off and be done with it. The events change the nature of the game, so enjoy them for what they are or else don't play with 'em.

I suppose I can see the annoyance on such a huge game (I tend to play nothing bigger than large maps for most of my games), but all the same, if they were only as powerful as the toughest civ, wouldn't they still trash your starbases? And in that situation, would they not end up only hurting the civs that are already not number 1? The #1 nation could fight the pirates 1:1 while the others would get blown away. That wouldn't upset the game - it would simply guarantee that the #1 military would reign supreme.

On the other hand, I'd be all for an option for different levels of events. Or even options for each specific event. I think events like the plague are almost totally worthless (so easy to survive) while events like the Jagged Alliance are much more interesting, and then events like PKs and pirates are almost terrifying in their ability to upset a game's balance.

Ah, last time I had the pirate event (Immediatly after the worst of the organised crime event was pver.) the pirates covered the map with their invincible fleets and shot at anything (including the waves of hostile transports that were crossing the vast nothing between star clusters.) that came within sight. They pretty much destroyed whatever I sent to remove the ones in inconvenient places.

The answer to my problems was just pouring everything into getting medium and then large hulls to destroy them. I also lured the pirate fleets to my military starbases, until the advent of large hulls made such a tactic redundant.

I was, initialy, doing quite badly in that game but the two mega events improved things significantly.

Whenever I get a ridiculously bad Mega Event, I load my last Auto save.

Horrible Mage Events:
Pirates (depending on time of game and tech of pirates)
Peace Keepers
Massive Strike causing all your plants to have spies on them

I haven't had the Peacekeeper event, but at one point I got the Jagged Knife event like three times in a row. It very nearly got me to turn off Mega Events, that one is just irritating--what, some of your worlds at random just magically get captured by enemies and there's no way to prevent it at all? If it's the wrong planets--and in my games, it was pretty bad--it can really screw you, especially if your tech/military isn't up to recapturing them. The hell with that noise. Time to reload.