so apparently i've learned now that the number of undead siegers sent by necromancers varies with wealth. Its year 2 late autumn now in my second successful evil embark. CherishedShades is doing well, 2 of the 3 cavern levels are breached and under control with the entrances cage trapped and seal-able and exploration shafts walled off; the third cavern layer's door is under construction.
Thanks to a magma pipe that extended all the way up to the first cavern layer, i now dont need to build my minecart system all the way down to the magma sea, and so i've started actively colonizing the first cavern layer so i can get my magma forges up and running. Hundreds of rock blocks were built to seal off the magma pipe, and to surround it with roof and wall, it was alot of work, the pipe must have been at least 30x30 and its almost sealed off, but not completely yet.
However since construction is not complete there are many holes in cavern level1's defense, and i cannot lock it down completely without sealing off all cavern access. To make things worse, a flying forgotten beast attacked me during the summer of this year. I was completely caught off guard since it was only second year, i didnt even have 80 population yet (could not see wealth since i dont have an appraiser) but i was pretty sure im under 100k wealth since i didnt even make weapons/armor yet, or any gold items. i've only made a few glass terraniums for cage traps using my single magma glass furnace and some masterwork green glass spikes for my slaughter chamber and for trade. Luckily the forgotten beast was only a blob made of ash, with no special attack, and so died easily to the few marksdwarf migrants i got.
now to the present, the siege at the late autumn of second year was one of the funnest, and its still on-going in fact. After the dwarven caravan arrived and began setting up shop, a siege of about 50 undead showed up and started coming towards the fortress. I quickly tried to get my dwarves to pull a lever and seal the depot, but they were too busy smoothing walls (i have the wall smoothing labor on almost everyone). And although the undead were slow, the trade depot was actually the shortest route into my fort, and so a couple of kobold thieves tried to sneak in through the depot entrance. This resulted in some fun as the caravan guards started chasing the kobolds, and chased them right out the depot entrance and soon into the hordes of undead.
One of the kobolds actually managed to get away (their dam fast) and the caravan guards fought valiantly, managing to kill about a quarter of the undead, but suffered casualties. Then more fun arrived, 2 goblin ambushes ended up attacking the undead siege from the other side of the map, and by the time they were finished, most of the undead were dead. They also finished off the caravan guards that were still outside. Somehow 2 caravan guards managed to retreat all the way back to the depot, and it just so happens there were baby snatches about too. Some of the snatchers used the normal fort entrance and were caged, but another one was caught by the merchants and killed. However, the snatcher caused some of the merchants to make a run for it, and it was at this unfortunate time that my dwarves finally decided to pull the retracting bridge lever that sealed off the depot.
2 merchants and a caravan guard were locked outside and had to use the normal entrance to get back inside, however, the goblins were trying to use that entrance as well, and were fighting against undead trying to get through. All over the map, the undead were coming back to life due to the evil land, and eventually the second squad of goblins retreated after some casualties and after the first squad was all dead/caged. The merchants and the guard that was locked out ended up dieing and the merchants inside now refused to trade with me. Tearing down the depot and forbidding the main entrance's hatch since all cage traps in the entrance were now exhausted, i watched as even the dead corpses in the neutral part of my map, near the center, started coming back to life.
Only 2 of the necromancers were caged, and im pretty sure there were at least 2 more hidden, and with the entrance locked, they now wander around the map, reviving corpses that didnt revive on their own. The last actions i took before saving were to order my dwarves to collect more sand for cages, and setting out the dig blue-print for an improved version of my cage-maze trap.