Void Art Feat

After intense study and sudden enlightenment you’ve mastered the true essence of cutting through space itself. You gain the following benefits:

Prerequisite: 4th level

• Part Magic. When you succeed on a Dexterity saving throw against a spell or similar magical effect and you would take half damage, you can use your reaction to cut the effect from existence around you, taking no damage instead.
• You gain the special Void Strike action (below).

Void Strike - Active Ability (Action, Supernatural)

• As an action, you can make a special attack that strikes at the dimensional boundaries around a creature, disrupting them and potentially briefly pulling that creature into the ethereal plane. The target makes a Charisma saving throw. On a failure, they take force damage equal to 2d6 + your Mystic Path modifier and are banished to the ethereal plane until the start of your next turn. On a success, they take half as much damage and are not banished to the ethereal plane.
• The creature cannot move while on the ethereal plane, but can otherwise take any action they can normally take, but they cannot interact with things on the material plane unless they normally could. You can choose to do no damage with this ability, and the target can choose to fail their save. The number of d6 damage dice the target takes increases when your proficiency bonus increases, remaining equal to your proficiency bonus.
• Once you use this feature, you cannot use it again until you finsh a short or long rest.

Source: KCLL, page 194

Mystic Path Feat Save DC:

• Any time a mystic path feat requires an ability score modifier for spell attacks or saving throws, use Constitution as the modifier. The DC is calculated as 8 + your Constitution modifier + your proficiency bonus.
• If your class grants you a spellcasting feature, you can use that ability modifier for calculating spell attack rolls and the DC instead of Constitution.