Answer:
I can be cracked made told and played.
A single syllable do I claim black was my most famous name; Fetal to mortals here below thousands have I slain in a single blow.
I am a king who's good at measuring stuff.
What is at the end of a rainbow?
I am the kind of nut that is empty at the center and has no shell.
If itβs information you seek, come and see me. If itβs pairs of letters you need, I have consecutively three. What am I?