Permanent Shield
The Permanent Shield perk is a small shield that will make smaller projectiles bounce off it. It will break after a certain amount of damage but reappear a short time later.
Tips
Damaging projectiles bounce off of shields, potentially hitting enemies or explosives.
Due to its smaller size, the shield may not always protect you from very high-velocity or large-hitbox projectiles.
The shield is damaged by Levitation Trail sparks, even though you are not.
Stacking
Permanent Shield stacks with Energy Shield spells for increased protection.
Each stack will result in more layers of shield which must be broken individually, giving several layers of resistance to projectile damage. Higher stacks also create a larger radius for each shield.
Whilst only 5 will appear by default in Holy Mountains, it is possible to get over 100 shields (spoiler), and even possible change their colour (spoiler). There is no limit to these.