Warlock: The Planar Guardian

You have made a pact with a powerful guardian of the planes. Such an entity seeks to hold back the denizens of other realms from freely spreading their influence throughout the multiverse, and to protect their home plane from outsiders. Some patrons actively seek out and destroy evil, some prevent planar travel by those who would misuse it, and still others simply slay any intruders into their plane of residence. Regardless, this entity has shared with you some powerful tools for defending the planes.

Entities of this type include Bolothamogg, Him Who Watches from Beyond the Stars; solars; empyreans; sphinxes; or even astral dreadnoughts.

Planar Sentry

Starting at 1st level, you gain the ability to sense the influence of other planes. As an action, you can focus your attention to detect such energies. Until the end of your next turn, you know the location of any creature from a plane other than the one you are currently on within 60 feet of you that is not behind total cover. You know the plane they are from, but not their type or identity. Within the same radius, you also detect the presence of any place or object capable of enabling planar travel, such as a portal or a cubic gate, as well as what plane(s) it leads to. If it leads to a demiplane, you learn that, but not any additional details.

You can use this feature a number of times equal to 1 + your Charisma modifier. When you finish a long rest, you regain all expended uses.

Entrusted Guardian

Also at 1st level, you acquire the training necessary to effectively defend yourself. You gain proficiency with medium armor, heavy armor, shields, and martial weapons.

Staunch Defender

At 6th level, your patron instills you with the fortitude to stand against the might and influence of extraplanar entities. You have advantage against being charmed, frightened, or possessed by aberrations, celestials, elementals, fey, fiends, and undead. Additionally, whenever a creature of one of those types makes an attack while within your melee range and you are wielding a weapon or shield, you can use your reaction to impose disadvantage on that attack. You can use this feature a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.

Multiversal Warden

At 10th level, you obtain the power to imprison a creature on their current plane, so that justice may be inflicted upon them. As an action, you can force a creature within 120 feet of you that you can see to make a Charisma saving throw against your spell save DC. On a failure, that creature is unable to use planar travel or teleportation, whether through spells or portals, for 24 hours. The creature can still be unwillingly forced to move to a different plane or location, such as by the Banishment or Plane Shift spells.

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

Interplanar Champion

At 14th level, you gain the ability to defend the planes even against native threats. Whenever you banish a creature native to the plane that you are on, you can banish it to a harmless location on a plane you specify, rather than a harmless demiplane. If there is no such location, then the spell fails. If the target remains there until the spell ends, it does not return. Additionally, your Staunch Defender traits now apply to all creature types, and you also have advantage against being banished.

Expanded Spell List

The Planar Guardian lets you choose from an expanded list of spells when you learn a warlock spell. The following spells are added to the warlock spell list for you:

1st
Detect Evil and Good, Bane
2nd
See Invisibility, Calm Emotions
3rd
Spirit Guardians (the guardians appear in a form of your choosing), Leomund's Tiny Hut
4th
Guardian of Faith (the guardian’s symbol represents your patron), Mordenkainen's Private Sanctum
5th
Banishing Smite, Hallow