Lets imagine for a moment that you have an arcanist or wizard with access to any spells of up to level 6-7. Assuming you have as much time to prepare as you need and it doesn't see you coming, or know you even exist.
How can you, alone, deal with this menace using the spells you have available to you, gold and various handy items?
The selective antimagic aura would stop fireballs quite nicely though.
You will want greater invisibility and fly so as to not lose the fight.
To win the fight: easy & dumb, but legal method: calcific touch + reach spell. Repeat until it's dex is drained to zero, should take ~5 hits.
Harder, but still doable: cast elemental bombardment and pelt it with earth elementals. This may take a few scrolls, the stone colossus has a lot of hp and can get fast healing 20.
Constructs are not subject to nonlethal damage, ability damage, ability drain, fatigue, exhaustion, or energy drain. Constructs are not at risk of death from massive damage.
Once per round, you may deliver a touch attack that inflicts 1d4 points of Dexterity damage and slows the target (as the spell) for 1 round.
Your suggestion don't work.
Your suggestion don't work.
You're right the first suggestion I made doesn't work. The second does.
I use blood money and simulacrum to make 10,000 pit fiends and those guys fight it for me
So, every day for the next 27+years you will cast your 2 spells and take 1d6 damage plus 10 Str damage. Then at the end of your 12 hr casting day you scarf down some food and limp through town with your 1-2 Str to find a cleric who will cast a full restoration on you at a cost of 2900 gp. So having spent 29,000,000 gp on restorations and 27 years of your life, you win.
While the casters are all pondering the implications of attacking a moving fortress, the lvl 16 Myst Str chugs a potion of invisibility and sneaks to within 100ft of the thing. He quietly set up his +1 distance double hackbut, steadies his aim, and takes a single shot (Dead Shot Deed). Using his cyclops' helm he makes the attack roll a nat 20 and crits the monstrosity. The walking fortress takes 32d12+112 damage, averaging 320 damage. Thus converting a mythic walking fortress into a standard one, he folds up his weapon and waves for the movers to begin moving his belongings into his new keep.
This is fairly simple. The selective anti magic shell is bypassed by force or earth descriptor spells. Dazing Battering Blast will prevent it from acting for 3 rounds at a time and do 10-15d6 damage per cast depending on your caster level. You can add in a tar pool for some extra damage while you throw empowered and dazing battering blasts at it.
Yeah. Daze locking it will probably be best. Battering blast is a nice choice because you can lesser rod the daze part. This will give you enough castings to get the job done while maintaining the daze. You could even with the right build make it a persistent battering blast for the same 3rd lvl spell slot and use the dazing metamagic rod.