Charred fortress spikes now indestructible?

[I am not real.]

Are the spikes on the charred fortresses now indestructible, or have they been buffed to several thousand HP? I took over a fortress and want to make it my own, and am trying to clear the spikes from the central tower. I've been wailing on it with fireballs and the black metal pickaxe for thousands of HP, to no avail, despite it showing damage numbers. Thanks.

[Draconis]

At least the spikes on the outer wall still break. I broke some by accident with my demolisher yesterday.