I've breached hell a few different times. lol I encountered it relatively early on - without spoilers from the community.
As I taught myself how to play through trial and error, I'd never heard of adamantine or demons or HFS until I unexpectedly encountered it. It was in my first successful fort - got it all the way to year seven, the king came, I was happy. Huge place, defended by moats, ballistae, pump systems - I went overboard with everything (defense has always been one of my favorite parts of the game) and oversized it to the point that half my fort was basically the entrance. I got 200 dwarves, and was pretty pleased with myself. Framerate sucked like anything, though... But anyway.
I had dug very, very deep... Still hadn't encountered magma in any of my games, so I didn't know it existed. The map was deep - roughly around 175 z-levels. But then around z-level 50, I found it... My first pillar of adamantine. I mined out the first layer and was awed at how much it was worth, set dwarves about extracting strands from it. Then I looked on the wiki... The first part was all "no spoilers, this is what it does". Then there was a major spoiler section... I hate spoilers. I didn't read it. I went back and mined out all I could upwards until it ended... Then I went back and mined down.
Just 5 z-levels down I hit the clown car. It was a relatively small number of demons, but I wasn't ready for it. The central staircase connected directly to the level I'd found the spire, and it was a matter of seconds before I had 40+ demons ransacking the main area of my fort, breathing fire. I panicked, of course... lol My single legendary spearwoman (gained in battle/training, didn't know about danger rooms) managed to kill just one of them, her 50th or so kill - and then she melted. It was only minutes before my fort was down to the last survivor - a hunter outside the fortress walls. I considered savescumming, but I felt it'd come to a fitting end, and I left it as it was until everyone was dead.
HFS is fun. lol
After the first encounter, I've always kind of wanted revenge on them... Second time was a near-miserable failure, 100+ webber/fire demons in a 13 year old fort (the max is NOT 80). Third time I almost made it - only 50 demons against a fortress of dwarves who had
all been trained in combat. Unfortunately, a goblin siege showed up at the same time and rushed into my fortress. Didn't have any dwarves to pull the levers and they got in. Attacked from two sides, everyone fell. These demons didn't breathe fire or webs - I would've won if it hadn't been for the goblins. Fourth time was the result of a cave-in. >.> Whoops. Obviously wasn't ready.
Just make sure the gates are closed before you begin, Mitch. lol If you're going to release them. Oh, and no, fortifications don't work. They won't path to them because they can't path around them. However... Demons tend to stop at any doors they can find to pull them down, even if there are dwarves nearby. You might be able to use this to your advantage.
I never tried the checkerboard, ThatAussieGuy - always wanted to do it "legit", with pure dwarf power.
Talvieno's basically the reactions guy out of the three of us
I do creatures, too, Splint. lol I did 30+ for the corpse fortress mod I'm working on on and off, and I did the scythods and manamaids too. Though I will admit, Mr Frog's creatures tend to be better than mine.
I have no godly idea how to make grave titans grow to proper size, and quite frankly I wish i could set it so adult Grave Titans were a rare encounter.
[BODY_SIZE:(insert adult year here)
:(insert days into adult year here)
:(insert desired body size at this age)
][FREQUENCY:5] (will make them rarer to come across)
[POPULATION_NUMBER:5:10] (will make far fewer total to come across - killing 5 to 10 means no more grave titans, if I understand right)
[CLUSTER_NUMBER:(min)
:(max)
] (number of creatures to appear in spawned group)
That should do it for you.
Spearbreakers II would be absolute madness, Sus. I'm kind of scared of it. Radioactivity by itself is a complete game-changer. You have to sort out the fast dwarves from the slow ones, the dizzy ones can't be warriors, the strong ones make better warriors, the biggest mutants can wield larger human weapons, the ones oozing blood tend to die eventually... It's wild. Swelling makes them bleed, too, if it's severe enough, though it doesn't mention that in the wiki... Honestly I think I'm almost against radioactivity being used in a Spearbreakers sequel. I like the idea of the new weapons and creatures, though.
And Aseaheru: I have a habit of making long posts.