Ring of Warding

A Ring of Warding is a magical ring that protects the wearer with a shimmering shield. The shield must be activated, presumably using an action, and it prevents a wearer from taking any damage from physical attacks, spells, and other magical effects. The shield apparently moves with the wearer, unlike the barrier created by a Globe of Invulnerability spell.

Trent Ikithon owned such a ring and used it when attacking Caleb Widogast and the Mighty Nein at the Blooming Grove in 836 PD, at the end of Campaign 2. Its shield was dispelled by Caleb using Dispel Magic, and the ring was taken by the Nein after they incapacitated Trent.

Trivia

 * The mechanical effects are as if the wearer is under an Invulnerability spell, but it is unknown if the ring literally casts this spell.