Domain Expansion

You create a hand sign whilst chanting; 'Domain Expansion.' You create a sphere in a 120-foot radius around you, of which is inescapable, but is breachable from the outside with an Arcana check equal to or higher than your Spell Save DC (a circular hole with a diameter of 10 feet). To outside creatures, the domain is an immovable floating black sphere. All creatures in the area are dragged into your Domain; a large dimension twice as large as the outside sphere. Your domain's effect depends on your Sorcerer's Sorcerous Origin:

Abberant Mind (DE: Mindscape). Your Domain Expansion is the palm of a great deity so powerful and ancient its true form is incomprehensible to mortals, floating in the furthest grasps of space. Every turn, all creatures, except those within 5 feet of you who you consider allies, must make an Intelligence saving throw or take 4d8 + your Charisma modifier psychic damage and are frightened of you until the start of your next turn. On a successful save, you take half damage and are no frightened. Additionally, while in your Domain, you benefit from all four benefits from your Revelation in Flesh feature.

Clockwork Soul (DE: Principle of Magic). Your Domain Expansion is a replica of the plane of Mechanus. Whenever a creature, except those in a 5-foot radius of you, who you consider allies, casts a spell, its die rolls are all minimized (unless if rolling an attack roll), and you can also choose the effect of any chaotic force (like Wild Magic). Additionally, once every turn, when you cast a damaging spell, it affects all creatures in the Domain Expansion, except for those in a 5-foot radius of you, who you consider allies. Finally, while in your Domain, you benefit from your Trance of Order feature.

Draconic Bloodline (DE: Wyrm's Bastion). Your Domain Expansion is the lair of whatever Dragon Ancestor you have. Every turn, all creatures, except those within 5 feet of you who you consider allies, must make a Dexterity saving throw or 6d8 + your Charisma modifier damage, the damage type being dependent on your Dragon Ancestor, or half on a successful save. Additionally, while in your Domain, you benefit from your Elemental Affinity feature.

Divine Soul (DE: Holy Sanctum). Your Domain Expansion is a place of worship, depending on your religion/source of divine power. Every turn, all creatures, except those within 5 feet of you who you consider allies, must make a Wisdom saving throw or take 4d8 + your Charisma modifier radiant or necrotic damage and be affected by the spell bane until the start of your next turn. Additionally, while in your Domain, you benefit from your Favored by the Gods feature for every attack roll.

Lunar Sorcery (DE: Nightly Lights). Your Domain Expansion is the Moon. Your Domain's effects are based on whatever phase you're currently in.

Full Moon: For the duration of your Domain, you cannot drop below 1 hit points and when a creature would have dropped you to 0 hit points or below, they take 5d8 radiant damage (damage can only be activated once a round). Every time you would be dropped below 1 hit point, the remaining turns left of your Domain is reduced by one (can only be reduced once a round). Additionally, while in your Domain, you can cast any 1st level Abjuration or Divination spell without expending a spell slot.
New Moon: For the duration of your Domain, all creatures, except those within 5 feet of you who you consider allies, are blinded and every turn, all creatures, except those within 5 feet of you who you consider allies, take 4d8 radiant damage. Additionally, while in your Domain, you can cast any 1st level Enchantment or Necromancy spell without expending a spell slot.
Crescent Moon: For the duration of your domain, you are under the effects of mirror image (mirror images cannot be destroyed), and when a creature, except those within 5 feet of you who you consider allies, misses an attack roll, they take 4d8 radiant damage, or half on a hit. Additionally, while in your Domain, you can cast any 1st level Illusion or Transmutation spell without expending a spell slot.

Shadow Magic (DE: Spiritual Requiem). Your Domain Expansion is a large graveyard with swirling spirits eerily gazing upon caught victims. Every turn, you can create one shadow, of which you can control. Every shadow has an initiative of 10 (losing initiative ties). Each shadow created by your Domain disappear when your Domain ends. Additionally, while in your Domain, you benefit from your Umbral Form feature (even if you're not level 18 because you get 9th level slots at 17th level).

Storm Sorcery (DE: Eye of the Storm). Your Domain Expansion is the eye of a giant tornado, with lightning flashing all around the swirling air. Every turn, all creatures, except those within 5 feet of you who you consider allies, must make a Dexterity saving throw or take 4d8 + your Charisma modifier lightning damage, or half on a successful save. Additionally, while in your Domain, whenever you cast a leveled spell that deals lightning or thunder damage, you can add your Sorcerer level to the damage roll.

Wild Magic (DE: Storms of Discord). Your Domain Expansion is a sea of raw magic, where all can simply walk on the magical waters. On initiative rolls of 15 and 5 (losing initiative ties), roll on the Wild Magic Surge table. Spells cast like this, if specified to be cast on yourself, you can instead cast it on any point in your Domain. Additionally, every turn, all creatures, except those within 5 feet of you who you consider allies, take 3d8 damage. The damage type is chosen by the roll of a d8. See the table below.

1 - Fire
2 - Acid
3 - Cold
4 - Force
5 - Choose either lightning or thunder
6 - Necrotic
7 - Radiant
8 - Choose either bludgeoning, piercing, or slashing.

Finally, while in your Domain, whenever you roll on the Wild Magic Surge table, you can roll thrice and use either number.

Domain Clashing:

If a creature already in a Domain opens their own Domain Expansion, they perform an Arcana contest with the caster of the original Domain. For the next minute, every round on an initiative roll of 10 (losing initiative ties), this Arcana contest is repeated, and the effect of the winner's Domain is played until the next Arcana check. When someone loses the contest, their Domain's effect doesn't take place until the next contest. Regardless of who wins, the visual Domain is a combination of both Domains. For example, an Abberant Mind and Wild Magic Domain Clash could have the deity's hand in the seas of chaos.