Angel's Blessing
Insert some overthinked lore stuff here.
It can be found in chests generated within Village Temples, Jungle Temples and Desert Pyramids.
While equipped in Spellstone slot, it will give the bearer immunity to fall damage and will redirect any projectiles in their closest proximity away from them. When triggered, it's active ability will instantly accelerate you in the direction you are looking, adding up to previous velocity.
Even though it's active ability can be quite useful on it's own for jumping over large gaps, high walls or even making double jumps - it was initially designed to work with Elytra.
In fact, acceleration works with completely different algorithm when player is flying using Elytra - the force of acceleration is calculated based on current velocity, and will be added to it. As player's speed rises, acceleration from Angel's Blessing becomes expotentially less effective, to prevent infinite acceleration.
Still, it can be used to enter the flying state from even flat surface, achieve great height and speed, and easily regain it after loss of momentum, also significantly increasing maneuverability. This allows for basically infinite and much more controllable flight than is achievable with conventional means, like firework rockets.
Angel's Blessing ability to redirect projectiles does not affect Wither Skulls.