# the rod that struck you is broken

"the king that sent his army against you is dead" or "the army that attacked you is defeated"

# For out of the serpent's root will grow an adder ... his offspring will be a fiery flying serpent

These two phrases are both the image of a serpent's offspring being even more harmful than the serpent. They represent a king's successor being more powerful and cruel than the first king. 

# an adder

a kind of poisonous snake

# a fiery flying serpent

"a quickly moving poisonous snake"