The only reason why a human being, a child of God, would die for the sake of his or her worst enemy, the devil, is that he or she has been tricked by the devil. The devil lures people away from their own good interest. The reason why they die is not martyrdom because the soul of that human would never would have agreed to die in the hands of the enemy. The soul of every human comes from God. Someone who “would die for Satan” is not doing what they truly, naturally want, but what the devil forced them to do even if they imagine that they are doing what they want. Satan does not offer freedom. He is the opposite of freedom. So a free choice under his influence is not possible.
With God freedom is possible. Martyrdom means freely sacrificing oneself so a free choice is necessary. Spiritual freedom is only possible with God so martyrdom is only possible for God.