Simple: Either a rare shipment artifact, or a relatively cheap CT lab artifact. It dose 400 damage to the target it is fired at - Can be used on players, NPCs, and based.

Cannot be used on players under the the effects of a calming amplifier, or a halcyon aura.

Possibly can be upgraded into a Thetacron missile (Dose 2,500 damage) via a mission.

A-There is no such thing as a "rare" artifact shipment, they are all weighted equally.
B-Everyone over about 500 should be hitting for 400+ pretty near every shot.
C-No way would that be worth the MILLIONS of research points needed to unlock in most CTLabs

Depends on what you're hitting. That could be pretty useful against higher level Bases. Level 5s with maxed defense are probably the ones that take the least damage, so a hundred or so of these would be pretty handy....

Unless the arti is limited to x amount per thingamabob, I can see alot of people saving alot of energy on things that require a ton of energy.

way too OP bases have a small chance of surviving as it is right now. low ranks barely have 400 hull so one shot and they die. -1

Fairly neutral on the idea. Kind of like it.

Also worth mentoning it would circumvent the low damage cap of small ship builds (The whole reason for small ship builds)

This only works if the weapons yield of he missile is weighed against the size of the target or something to that effect. Smaller ships take less damage.

This is not a good idea, first off people will stack up hundreds of them and then use them on one base, utterly destroying it. Secondly in any quantity other than hundreds/thousands, the arti is utterly significant, saving you what? 5? 10? Energy, if that. So a big fat -1.

I think the idea is sound and has merit. It just needs some tweaking.