If you use a smaller fleet, it might warp into a Unbidden meatgrinder of five space stations, 5.0 k each, and that's just wasteful. Once you find them, immediately right click and order your biggest fleet to hunt them down. Step three: Begin the tiresome hunt for their construction units, and destroy them. But remember the geography of a sector matters, so figure out which corner you can jump in on so to quickly overwhelm the wormhole, then cross your fingers and roll the dice. The Unbidden take a curiously long time to respond to these, in one case they left one up entirely untouched.
Jumping into the wormhole itself is tricky, and for me involved building wormhole stations under fire protected by diversion fleets.
Once you do this, you'll be stunned at how quickly they melt away. SO: corvette and battleship spam, together, overwhelms their targeting and forces them to disperse their fire, giving you enough time to breeze through their stacks. But as someone else here said, if you can't point-target the warpgate itself, neither can the static-y bastards point-target your battleships. Tangent: The problem, really, is the targeting mechanic. The target rich environment completely baffles them. The other possibility is both neater and messier, and involves a suicide fleet of both battleship AND corvette spam, dumping a fleet of about (in my case) 66 battleships, 30 destroyers, 33 cruisers, and 66 'vettes on their wormhole. To counter their short-range superiority, two schools of thought have emerged: one advocates tiresome (but effective) hit and run tactics, using Tach Lance battleships to warp in, wipe out their fleets, and then emergency FTL once the Unbidden get in range. They're really, really powerful up close, and I want to spare you the agony I suffered last night watching my 80k fleet slowly melt into 4 limping battleships. Eventually you'll be caught out at range, and destroyed.
I made a huge mistake taking my time warping to their wormhole, gradually chewing up their fleets but never, of course, regurgitating reinforcements like they could. Step two: Apply DIRECTLY to the wormhole. The result will really put your fleet into fallen empire territory tech wise.) So, while your fleet is keeping them busy, switch to Passive on a science vessel and throw in a young 2-star to research their debris. Tangent: ALL of these techs- matter disruptors, shield capacitors, etc.- will be researchable once you take out one or two Unbidden fleets.
#Unbidden stellaris series
I also loaded out a series of 'vettes with matter disruptors, shield capacitors, and hyper shields. Here's the fleet OOB that got me a win: 66 battleships, 33 of which were Tach Lances, Aggressive AI computing, 22 of which were quantum torpedoes and devastator torpodoes, the remaining were equipped for point defense. I lost 3 fleets, one of 40k, one of 60k, and one 80k this way). Step one: build a suicide fleet of about 100k. If you have any further questions I'd be happy to answer: After much frustration I happened on the solution this way. This is a much harder process than many 1.1 vets seem to think, and everyone has an answer.