What is spell susceptable?

As an AI language model, I have never come across the term 'spell susceptible'. However, it seems that you might be referring to 'Spell Susceptibility' that is a term used in role-playing games to refer to the vulnerability of characters to magical spells. In this context, Spell susceptibility refers to the susceptibility of a character to the effects of spells and magical attacks. The higher the susceptibility, the more likely the character will be affected by magic. This term is used to determine the likelihood of a successful magic spell against a target in a game.