Planar avatar warlock patron

[chevyboys]

Fair warning: you are going to think this is bad.
I'm running a campaign where a player is playing host to a planar avatar. If you have read Brandon Sanderson's Novella for magic the gathering, the bog is sort of the inspiration of these. I'm trying to create something that would be sort of on par or a little bit better than a feat, and want to get a balance check and some suggestions from the community.

This is only my 2nd homebrew ever, so please be kind. I'm still pretty bad at this.

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Boring Lore stuff
The planar avatars, the first children of the three dragons, are the sentient remnants of the combined creative powers used to create each plane. Each of them has several abilities, depending on how close they are to their original plane. Most need a living host to move on locations outside their planes. Several were imprisoned on the prime material plane, weakened for millennia by this separation from their homes, in places that slowly became suffused with their power. Each of these can be a warlock patron of a type chosen by your dm, but must be within one mile of their host and the warlock in question for the warlock to successfully draw on their power if the avatar is not on their home plane. The planar avatars each seek to return to their home plane, where they can move without the aid of a living creature, and are nearly immortal and omniscient. If they can get a mortal to take them to their home plane, then they will be free. Sadly, if this were to ever happen, the amount of power released at that event would cause Kyber itself to awaken from it's slumber, and the tremors would be felt in every plane.

Hosts gain the following abilities: at the cost of gaining 2 levels of exhaustion, and with the cooperation of the full avatar, as an action they can:

Invoke the plane: Make the plane associated with the avatar semi-cortanimous, bringing effects of that plane into the surrounding area. This zone has a radius equal to 10*ECL of the host. The host suffers no adverse effects of the cortanimus plane. Creatures of an opposite elemental affinity or alignment of the plane suffer disadvantage on all attack rolls and ability checks while in this area, and creatures of the same alignment gain advantage on the same. In addition, one of the following effects may be chosen, each lasting up to one minute:

• Physical planar manifestations that deal 1d12 damage per 5 levels in warlock the host has to all creatures other than the host in the area
  
• 1 minion of appropriate type for the plane may be summoned. This creature is hostile to all creatures except the host,
  
• The host is wreathed in the essense of the plane, and gains resistance to all nonmagical damage, and immunity to damage that is aligned with the plane.
  
  

Escape to the blind eternities: The host and their worn and held possessions are flung to a random point on the astral plane, by using the avatar's connection to another plane to rip them away from their current plane.


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Avatar individually granted powers:
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In addition to the exhaustion causing effects listed above, Each of these spells is usable twice per day, and uses the host's charisma and warlock level respectively to calculate spell effects. There are no components required for spells cast with this ability. If the host does not have any levels in warlock, or is a warlock dedicated to another being, they cannot use these spells.

Material Plane: N/A. There is no material plane avatar, as the material plane is made up from elements of all the other planes
Fey Wild: Enthral
Shadowfell: Darkness
Ethereal: Misty Step
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Air: Gust of wind
Water: Alter Self
Earth: bark skin
Fire: Flaming Sphere
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Astral: Idk guys, I'm going to need help here
Elysium: Zone of truth
Bytopia: Lesser Restoration
Mount Celestia: Prayer of healing
Arcadia: Gentle Repose
Mechanus: Hold person
Acheron: Spiritual Weapon
The nine layers: Scorching Ray
Hades: Ray of Enfeeblement
Carceri: Flaming Sphere
The abyss:Blindness/deafness
Pandemonium: Shatter
Limbo: Blur
Ysgard: Branding Smite
Arborea: Spike Growth
The Beastlands: Find Steed

[Mork]

Ok. So the feat is:

-1 lvl 2 spells useable twice a day.
There are some other spells that grant spells, those are useally only usable once a day, so you might want to downgrade that. Also instead of no material components, it might be nice to have as a material component something from the plane in essence. (really easy in the case of the air plane ;)).

-create an area of planar damage, summon an ally and gain damage immunity. for the cost of the exhaustion.
A). the radius now scales 10 (ft?)/lvl which is.. a lot. Starting level 3 you are covering almost the entire battlefield and at lvl 15 you can't use your ability in city anymore because you are killing civilians all around you. I'm a big fan of the new proficiency scaling, so I would go for 5ft/PROF bonus for 10 - 30ft range. or maybe 10ft for 20 - 60ft radius. (60 ft radius is ALOT)
B). Damage scaling seems fine, could change it for d6/proficiency, but won't differ much.
C). Immunity from the element is I think to strong, I think resistance would be good enough.
D). The summon is I think the strongest part of this ability. It will requires some CR associated with it I think. But If you are only going to use it in your homebrew you can think of this on the spot. There are some summoning spells that you might use as a guidance, but take into account for example a lvl 4 spells still only summons a CR 2 monsters. Maybe your lvl/4? rounded down is the MAX CR, and that is probably already on the strong side.
E). So the cost.. exhaustion levels.. This are not often used in 5e, except for the frenzy barbarian, and because of this the frenzy barbarian is often seen as the worst subclass. 2 levels exhaustion will probably mean the ability is only used against boss fights, in which the party has some indication that they won't be fighting the next day anymore. I understand that you want some cost associated with it, it's a strong fantasy. But from a game design perspective making your charachter worse disincetives it's use.
So.. I would say once a day/24h/LR/dawn. And then you could add 1 exhaustion level / 10 hp damage/ 2*PROF damage, in addition to the once a day thing

Overall the ability is probably better than any feat, but is seems like this a story reward more than anything? And I assume that it's not only one player that will get it, but that all/most players will get something like it (eventually). Than you just have to scale your combats accordingly. (and for to scale this I would add more combatent instead of stronger ones. You give AOE damage, and another combatent)