Head to the Core is a mission in Ratchet & Clank (2016 game) taking place in the Deplanetizer. After Ratchet and Clank used the Hologuise to sneak through to locate the gravity stabilizer, they also disabled all sanitation fields. The two then fought their way through the Deplanetizer to reach the core, and disconnect the gravity stabilizer, completing Elaris' plan.
At this point, the Hologuise will no longer fool enemies, so you will have to rely on pure combat. Head to the end of the room and use the Gadgetron vendor to refill ammo, then proceed through to the next room. Rather than heading up the grav-ramp on the left, defeat the warbots and versa-targets drop, allowing you to use the Swingshot to cross them. Proceed through the linear path to another room with two golden Drek statues full of warbots. Destroy the warbots and the robomutt reinforcements (consider using the Sheepinator against the robomutts, as it will clear them quickly, and other ranged weapons against the warbots). A door will open, with blarg space commandos and blarg elite commandos heading from it. Defeat them, but before you head through the corridor through the opened door, first look for two large rectangular crates with blue icons on them, and jump on the first then jump on the yellow ladder-like ledges on the right that lead up to the top of the room. Jump across the two floating platforms once they converge to reach the gold bolt. Afterwards, head through the corridor through that the door led to.
This corrdior is filled with enemies; clear them out to reach the large room with more enemies. Fight through here to the middle, to see the bridge is out. Head right to the bolt crank, and turn it to extend the bridge across. Before you cross, head left, and on a level platform above are two blarg bombthrowers. Climb the boxes stacked to head up and defeat them. From here, you can choose to use the turret to defeat remaining enemies, or simply use your weapons if you have more to upgrade. Either way, kill the warbots and a blarg armored transport will appear. Destroy it, along with the other warbots that arrive, and on far right at the end of the room is an elevated platform with two more blarg bombthrowers. Climb the two stacked boxes and head on top of the platform to obtain the final RYNO holocard, which will complete the set if you obtained all other RYNO holocards.
A door will then open with a vendor and two warbots; kill them and the mission "Disable the Gravity Stabilizer" will commence. A teleporter will activate, allowing you to return to your ship. Before you begin the next mission, return to your ship, and if you have not already, collect all RYNO holocards. Then, return to Rilgar and complete "Bring all RYNO holocards to dealer" to obtain the RYNO, the most powerful weapon in the game. Return here again.