So I already thought that Sea Glass Guardian could be a good aura, giving something like a Champion reaction to an ally being hurt, but without being a reaction and with being able to be triggered multiple times per turn. Doesn't do as much damage as say Winter's Clutch in a single instance but can trigger more often.
But now I am watching someone's youtube reaction to the playtest and they brought up a good point. What happens if you have Sea Glass Guardian up and someone uses an AoE like fireball, or some ability similar to Whirlwind Strike or Maelstrom Blast where they attack a bunch of targets in an area. Does each ally getting hit and taking damage trigger Sea Glass Guardian separately? Say you are level 20 and you have 5 allies with you in the aura, and an enemy caster either in the aura or adjacent to the aura casts fireball and deals damage to you and your five allies. Do they take 20 damage once, or 20 damage six times for 120 damage. Or more if they happen to be vulnerable to whatever type of damage your Sea Glass Guardian is set for.
The playtest doesn't specify but based in all others similar abilities that triggers with damage. If an AoE/multitarget effect affect more than one protected creature it's "reaction" only applies once per effect never per affect creature.