Human warships in general have an energy generating core which powers a multi-configuration shield and multiple directional particle weapons.
High Rank Beasts have the biological equivalent of the Human "Core" technology called Nohsim, which is a very compact high yield energy and particle generator, allowing them to project Personal Shields and to project particle attacks. These cores emit a distinctive signature when activated, allowing them to be detected.
There are different classes of cores, from C-Class up to S-Class. Then there's the massive core that's left over after the Blue Flower debris lands on Tobal.
Core Temple of the Central Order
"This is top secret... C.K.'s energy source was a Nova-Class engine of the floating fortress Avalon in the age of the Great War."
"Along with the Eden, it's the biggest power generator of mankind."
Avalon was a "Floating fortress with a Nova-Class black hole engine which fought against tens of flowers and billions of Ags hundreds of years ago..."
(Ep 0 - Ch 67)