Monks from the Way of the Horizon Monastic Tradition, thread the line between the Prime Material and Ethereal planes.

Detect Portal

At 3rd level, you gain the ability to magically sense the presence of a planar portal. As an action, you detect the distance and direction to the closest planar portal within 1 mile of you.

Once you use this feature, you can’t use it again until you finish a short or long rest.

See the “Planar Travel” section in chapter 2 of the Dungeon Master’s Guide for examples of planar portals.

Planar Fists

At 3rd level, you learn to draw on the energy of the multiverse to enhance your body. 

At the start of your turn, you can make either your hands or legs appear three times larger and radiate energy. For the next minute, all unarmed strikes you make with the affected limb(s) deal force damage instead, and you can spend 1 Ki point per strike to cause the target to take additional force damage equal to your martial arts die, after it is determined the strike successfully hits. Also during this time, and at the DM's discretion, you can spend 1 Ki point to gain advantage on any Strength(athletics) checks that are associated with the affected limb(s).

Ethereal Step

At 6th level, you learn to step through the Ethereal Plane. As a bonus action, you can cast the etherealness spell with this feature, without expending a spell slot, but the spell ends at the end of the current turn.

Once you use this feature, you can’t use it again until you finish a short or long rest.

Distant Strike

At 11th level, you gain the ability to pass between the planes in the blink of an eye. When you take the Attack action, you can teleport up to 10 feet before each attack to an unoccupied space you can see.

If you attack at least two different creatures with the action, you can make one additional attack with it against a third creature.

Spectral Evasion

At 17th level, your ability to move between planes enables you to slip through the planar boundaries to avoid harm done to you during battle. When you are hit with an attack, your can spend 2 Ki points to use your reaction and cast misty step, causing the attack to miss.