Chlorine.
Chlorine is called a green poison because it is pale greenPoissongas.
You think probable to chlorine.
you know how each dragons eyes match there scales which lead to there element? Well My theory is that because of Cynder's pale green eyes that she was suppose to be a pale green dragon making her a poison dragon.
Barium is used for rat poison.
"Green Poison" is a nickname for Paris Green, a toxic substance. It is used as a pigment, for insecticide, and as a wood preservative, but it is very poisonous.
no
arsenic
iodine
Arsenic
arsenic
Bromine