King of Magma Tremok

Earth Glide. The elemental can burrow through nonmagical, unworked earth and stone. While doing so, the elemental doesn't disturb the material it moves through.

Siege Monster. The elemental deals double damage to objects and structures.

Flame of Phlegethos. When you roll fire damage for a spell you cast, you can reroll any roll of 1 on the fire damage dice, but you must use the new roll, even if it is another 1. Whenever you cast a spell that deals fire damage, you can cause flames to wreathe you until the end of your next turn. The flames don’t harm you or your possessions, and they shed bright light out to 30 feet and dim light for an additional 30 feet. While the flames are present, any creature within 5 feet of you that hits you with a melee attack takes 1d4 fire damage.

Fire Adept. Spells you cast ignore resistance to fire damage. In addition, when you roll damage for a spell you cast that deals fire damage, you can treat any 1 on a damage die as a 2.

Investiture of Stone. You can move across difficult terrain made of earth or stone without spending extra movement.

Multitasker. Allows you to cast a second Concentration spell while already concentrating on a different one. Must pass a WIS Save DC 10. On a fail, any concentration spells you were already casting end. On a success, you cast a second concentration spell from your list of prepared spells.

Multiattack. The elemental makes two slam attacks, casts two cantrips, or one of both. 

Slam. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 19 (2d8 + 10) bludgeoning damage.

Fey Presence. Once per short rest, as an action, you can cause each creature in a 10-ft. cube from you to make a WIS saving throw (DC 22) or become charmed or frightened by you (your choice) until the end of your next turn.

Gaze of Two Minds. You touch a willing humanoid and perceive through its senses until the end of your next turn (with an action to maintain on following turns) as long as the creature is on the same plane of existence as you. You are blinded and deafened to your own surroundings.

Investiture of Flame. You fill you lungs with air to feed your inner fire. For the next 10 minutes flames race across your body, shedding bright light in a 30-foot radius and dim light for an additional 30 feet. The flames don’t harm you. Until the flames die down, you gain the following benefits:

• You are immune to fire damage and cold damage.

• Any creature that moves within 5 feet of you for the first time on a turn or ends its turn there takes 1d10 fire damage.

• You can use your action to create a line of fire 15 feet long and 5 feet wide extending from you in a direction you choose. Each creature in the line must make a Dexterity saving throw against your Spell Save DC. A creature takes 4d8 fire damage on a failed save, or half as much damage on a successful one.

Quake of the Living Mountain. You can use your action to create a small earthquake on the ground in a 15-foot radius centered on you. Other creatures on that ground must succeed on a Dexterity saving throw against your Spell Save DC or be knocked prone.

Spellcasting: Modifier (+10). Spell Attack (+20). Save DC (26). Tremok is a level 11 druid, and a level 9 warlock. 

Cantrips

Create Bonfire

Eldritch Blast

Magic Stone

Mold Earth

Produce Flame

Sacred Flame

Level 1 Spells (4 slots)

Arms of Hadar

Burning Hands

Earth Tremor

Greater Mold Earth

Hellish Rebuke

Level 2 Spells (3 slots)

Heat Metal

Scorching Ray

Spike Growth

Level 3 Spells (3 slots)

Erupting Earth

Spirit Shroud

Level 4 Spells (3 slots)

Fire Shield 

Wall of Fire

Level 5 Spells (4 slots)

Stone Stride

Contact Other Plane

Flame Strike

Planar Binding

Level 6 Spells (2 slots)

Move Earth

Sunbeam

Level 7 Spells (2 slots)

Fire Ball

Lightning Bolt

Plane Shift

Blink Steps. Immediately after you take the Attack action or the Magic action, you can teleport up to 30 ft. to an unoccupied space you can see.

Cauterizing Flames. You gain the ability to turn death into magical flames that can heal or incinerate. When a Small or larger creature dies within 30 feet of you, a harmless spectral flame springs forth in the dead creature’s space and flickers there for 1 minute. When a creature you can see enters that space, you can use your reaction to extinguish the spectral flame there and either heal the creature or deal fire damage to it. The healing or damage equals 2d10 + your Wisdom modifier. You can use this reaction a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.

3 Legendary Actions per round. 

1 Action. 

Cast a spell. 

Make a Slam attack. 

2 Actions. 

Perform a Multiattack. 

Active your Fey Presence. 

Ignite your Investiture of Flame. 

3 Actions. 

Regain spent Sorcery Points.