Another core suggestion. Just forget about reading this. Give it a -1 even though it's not google plus.
The core should be opened via an NPC standing in the Sanctuary requesting that knights drop their minerals into a gate after the Shadow Lair. Once a certain amount of minerals is achieved, the elevator to the core will open.
The core opens up into a Lockdown-style room. There will be a party pad and an NPC (from the Alpha Squad) telling the knights that there is a group of gremlins who just broke through the defensive barrier and are preparing to take over the core. That's right. You're going to play Lockdown against gremlins. Swarm gremlins to be precise. However, on your side, you'll have Emberlight gremlins to help you. And maybe the Alpha Squad. And Rhendon. And Biotech Han (whatever he'd do). And some of those slow FSC healing pads outside of the base.
Each CP will be permanently captured once a knight captures it. Each CP will also have a different theme (furnace, wildwoods, etc.). The gremlins will have precise AI's and will work together. Reviving will be instantaneous for the gremlins (at their base), but knights will have to revive by the good old Clockworks rules.
In the center of the room is a Swarm Seed surrounded by the runes seen near the Konjuring Kat. Once the knights capture all points, a wall of rockets will come down in such a way, forcing knights to flee to the base for safety. Gremlins can die or run. Once the knights are at the base, the Swarm Seed will spawn a Tortodrone or a Rabid Snarbolax or a group of Black Kats or something. Then the knights must run and capture all the points again, also defeating whatever spawned in the process. Rinse and repeat. At the end of, say, the fifth wave, Tinkinzar will spawn and... no, that's a bad idea. The core opens, you get 500 CE and a filled mist tank and get blasted back to haven because there's too much energy to handle. Then there could be a mission on how to safely handle raw CE.
Okay, I'm done. Go ahead and tear it apart now, you hungry wolvers.
xD Not sure how well this can be implemented but LD vs Gremlins sound crazy and fun. I kinda like it. :>