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 perform particle beam attacks. These cores emit a distinctive signature when activated, allowing them to be detected on sensors.
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 from 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 Beasts hundreds of years ago..." ME0-Ch67