Usage of Soothing Sunlight requires that the caster belong to the Princess's Guard covenant. It restores HP for 6 times MagAdjust for the user and also any friendly phantoms around them, including NPC summons and enemies affected by Undead Rapport.
Soothing Sunlight benefits from miracle synergy. Each level of synergy increases the healing multiplier by 0.25, increasing the multiplier to a maximum of 7.0
Given the fact that it requires membership of the unpopular Princess's Guard covenant and also the exorbitant faith requirement, Soothing Sunlight is a rare sight indeed. Also, it takes coordination for allies to get close to someone who is about to cast this miracle, and communications in Dark Souls is both time-consuming and limited. Ultimately, this limits Soothing Sunlight's practicality as a healing miracle.