How should i run monsters?

[zionspelunker]

So I'm relatively new to playing gurps, i've played in one campaign that got canceled due to covid and i've made some races and such in my spare time which ive been told were pretty well done. My question is if im going to try and run a one shot and make a bunch of monsters should i stat each and everyone out like a character or should i just give it abilities as i desire from outside the rules of the book? I'm specifically thinking of making a hydra with multiple heads growing back each time one is cut off but i dont know how much i should worry about all the nitty gritty stuff or how i should do it if i wanted to run a longer form campaign with a variety of weird and wacky creatures. Thanks for any assistance