As a Magic action, you can summon an elemental storm around you in a 10-foot Emanation. Choose Acid, Cold, Fire, Lightning, Poison, or Thunder damage. The Emanation lasts for 1 minute and ends early if you dismiss it (no action required) or have the Incapacitated condition.
Whenever the Emanation enters the space of a creature you can see and whenever a creature you can see enters the Emanation or ends its turn there, you can force that creature to make a Dexterity saving throw against your spell save DC. On a failed save, the creature has the Prone condition and takes 1d8 damage of the chosen damage type. On a successful save, the creature takes half as much damage only. A creature makes this save only once per turn.
The damage increases by 1d8 when you reach Martyr levels 5 (2d8), 11 (3d8), and 17 (4d8).
Once you use this feature, you can't use it again until you finish a Short or Long Rest. You can also restore your use of it by taking 5 Radiant damage (no action required). This damage ignores Resistance and Immunity, and bypasses Temporary Hit Points.