Helm of Astral Sanctuary

When the instant activated ability of each of these equipment cards resolves, it generates a shielding-prevention effect that prevents the next 1 damage that would be dealt to your hero this turn.

You cannot use this during a resolution of a card. For example, if a card says “Deal 2 arcane damage. Deal 2 arcane damage.”; you cannot take two arcane damage, and then use this ability because a card must fully resolve first before a player gains priority.

This prevents all types of damage including damage from attacks ( damage), arcane damage, and (untyped) damage. This does not prevent loss of life.