Oath of the Ghost monks are able to temporarily phase into the ethereal plane. They can use this to their advantage to dodge harmful attacks and strike back with unwavering speed.

Reactive Vanish

When you take this subclass at 3rd level you gain the ability to briefly disappear from the material plane. As a reaction from being attacked by an opportunity attack, you may spend 1 ki point to briefly vanish into the ethereal plane, causing the attack to have disadvantage. If the attack misses, you may then make an unarmed melee attack against the creature making the attack.

Planar Phasing

At 6th level, you are able to more easily harness the power of the ethereal plane. You can spend 2 ki points to cast blink. In addition, you can target creatures in the ethereal plane with your attacks.

Consecutive Strikes

At 11th level, you gain the ability to pass between the planes in a blink of an eye. When you use 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.

Ethereal Dodge

At 17th level you are able to willingly vanish to dodge even the most harmful effects. When you are targeted by a weapon attack or a damaging spell targeting you that does not deal psychic damage, you may spend 2 ki points to use your reaction to ignore the damaging effects of the spell or attack. Once you use this feature, you cannot use it again until you finish a short or long rest.