Tectonic Upheaval Device
Transforms an oceanic world into a Terra world by causing massive plate movements which thrust up landmass and expose valuable minerals buried deep in the crust.
Effect - Mineral resources improved by 2

This would add a lot without being too overly powerful. Imagine melting an icy planet, then turning it into a terra, then using a gaia seed.
Oceanics need some sort of upgrade potential.
Not sure where this item would be discovered... maybe an addition to the "pawlacite thaw" chain.

So 17x all mega-colossal ocean to 19x mega-colossal terra to 21x omega-colossal Gaia?

Except this item would have no effect on size

I know, that's why the mega-colossal ocean went to mega-colossal terra. The size change is from the Gaia seed.

maybe since it makes massive land masses rise, it reduces the planet's size by 1!!!!!!!

NO! I want a Omega Colossal planet! +1

Make planets any bigger and they might implode and create a black hole.

...But I want an Omega Mega Colossal as well!

That's dying stars you're talking about there.

Mass surface melters are awesome. But did you ever think about how, from a scientific viewpoint, they don't make since? Liquid water is denser than ice and will therefore take up LESS space than ice. So in reality, melting an icy planet would DECREASE it's size.

it's available area that can be built on, you try building things on ice.

Technically, it never says that oceanics are water. It could be mercury, bromine, methane, liquid hydrogen. Those would expand, according to science. Water is the exception.

But ice is defined as the solid state of water. The other solid state of homogeneous composition are called crystals(ice is a crystal too, it's just special and got its own name).
So while "oceanic" does not require water, at least the ones made from icy ARE water.
Now if you have a "planet freezer" or something.... I dunno~ it could go either way.

Another issue is with desert to crystal, which is very likely to be impossible. As long as the desert planet was not of similar composition throughout, it won't work. And frankly, if you are really able to change a planet on the atomic lvl(as opposed to molecular), you can change any solid planet(barren, volcanic etc etc) into crystals.
Then there is plasma planet.... which.... that's REALLY a star, not a planet.

In any case, back to the subject of the thread. Definitely +1 on the idea because it's reasonable and realistic
Other reasonable transformation would be:
volcanic to barren/crystal/desert (or maybe volcanic to barren and demon to crystal etc)
Gaia to Ecumenopolis
volcanic to Aphotic (it have a hot enough core, so if you teleport it.... err...)

I agree that an artifact transforming an oceanic into a terra would be pretty sweat.