Foundations

[waxen quarry]

Foundations for buildings
Literally a fireproof version of a keel that can only be placed on the bottom of a building.
Comes in regular, large, and grand varieties that are each equivalent to their respective keel except for not being flammable, and of course, only being placeable on the bottom of a building.

[fickle oxide]

keels were intentionally disabled/removed from buildings in the base to prevent late-game defensive battles to be a tedious chore to deal with, iirc, though could be interesting for a mod

[wary sequoia]

Maybe on top of this, a weaker vertical variant called pillars, or something? It should be walkable at the base, and every other tile up.

[muted marlin]

I like the idea of a pillar in the game

[fossil chasm]

I would be fine with it if it was hard limited to one, ie it cannot have anything to the sides or below it.