When you use it, are planetary structures destroyed? and does the planet keep it's new colony/recently invaded bonus?
I need to know because I'm 1 terraformer from my mission exotic, and need to know when to drop a locus on it.

no, buildings on the planet are not destroyed

if you're planning on ticking someone off... drop a locus on the planet immediately after invading, then use the hyperterraformer and planetary time vortexes

But... Unless there's already some juicy artifact buildings on an enemy planet, just colonize the crappiest planet in your list. And YES the locus MUST be used on a NEW colony to get the bonus.

*hem*omnibase*hem*

Why not invade the easiest/best arti one instead? Then you can locus it for +4 mining.

So I can Invade, locus and then terraform, and all the buildings stay?

if someone has an omnibase, i'd say invade, extract, and move that omnibase to a planet of your choosing
(that'll tick them off if they get the planet back and find it's gone)

as for the hyperterraformer... just invade a 0-defense very tiny extremely sparse.... as long as it's an invasion you get the locus bonus

and yes, yes, yes, yes, yes, oh God yes, all your buildings stay

FWIW, you should always use a volcanic or an icy. Just make sure you put on the Convoy Heat Seeker or Permafrost Network before changing it so you get the extra +1 mining/research.

and if you want your spires to be +2 mining (from the volcanic) or +2 arti (from the icy) instead of +1 all, place them before changing as well

I forgot to invade an icy and drop a locus on it, instead I hyperformered one of my own icys.

i invaded a metalic put the assimalation locust on it then dysoned it best decion ever would be almost as good on an exotic