Crimson Aegis

To cast this spell a living creature must expend one of their Hit Dice as they let themselves bleed into the rune carved into their own flesh. When the spell is finished the blood streams off the caster’s body and forms a hardened disk that hovers between them and anything that would harm them.

For the duration of the spell the caster gains temporary hit points equal to the Hit Dice expended and a +1 bonus to their Armor Class. If the caster is in direct sunlight they immediately lose the temporary hit points granted by this spell.