Grants a Body Buff that lasts for 15 seconds and increases the Physical Damage Negations by +35% (+10% against other players), decreases incoming Poise Damage by -34%, and prevents light stagger (which includes one- and two-handed light attacks, running light attacks, rolling light attacks, backstep light attacks, and jumping light attacks from non-Colossal, non-Great Weapon Classes).
Reduces the Tarnished's maximum HP by -5% when held.
Frame data
The Buff becomes active on frame 21/0.70 seconds in. The entire animation takes 50 frames/1.67 seconds to complete.
Since this item reduces a player character's maximum HP when held it's generally best to use it immediately after finishing the current dialogue with Fia.
It is possible to keep the item even with the HP penalty, but since it has a pretty weak Effect and is a single-use item the only reason for this would be sentimental value or for collecting.
See also
Radiant Baldachin's Blessing, an extremely limited (one per Journey) and much more long-lasting variant of this item, acquired at the end of Fia's questline.