New Battle Mechanics + Lightning Primal Powerful Creature Fight (Radiance)

Lately I've been experimenting with new battle mechanics to enhance the engagement of combat with Powerful Creature Combat.

Powerful Creatures are threats that have multiple turn initiative - each one dedicated to a specific action.  Dividing this up allows the creature to feel menacing - able to have it's turn scattered throughout the battle.  During that turn, the creature can only take a specific defined action and no others (they cannot move, attack, or take bonus actions unless specifically dictated by the turn).  This also allows players with a studious eye to plot with their party.

The introduction of this was the Lightning Primal.  I wanted each action to have significant weight, while allowing for players to activate different options to either bypass or alter the actions themselves - while still having alternative consequences.  This allows players not not necessarily choose a 'right' option - just an option that felt like the right one at the time.

This also introduced the reward of Vulnerability Stacks.  A creature who has a Vulnerability Stack has an effective token for double damage.  As a player, after successfully seeing if a attack or spell hit, may choose to double their damage from 1 source before rolling damage.  Once it is done, the Vulnerability Stack is spent.  A creature can have more than 1 Vulnerability Stacks.

With that I introduce the Lightning Primal.

Lightning Primal

AC 15; HP 180; Speed 60ft; Str14, Dex 20, Con 14, Wis 10, Cha 6; Damage Resistances lightning, thunder, bludgeoning, piercing, and slashing from non magical attacks; Damage Immunities poison, Condition Immunities exhaustion, grappled, paralyzed, petrified, poisoned, prone, restrained, unconscious.

Powerful Creature:  This creature is infused with great power, and is able to take the following turns in one round : Concentration, Move, Action, and Conjure.

Semi Intangible : Creatures may end their turn in this creature's space.  They are still effected by all attacks.

Concentration Turn (Initiative 20) - Call Lightning: This creature is able to Call Lightning. If they took Cold Damage, they must maintain concentration equal to the highest source of cold damage divided in half - minimum DC 10. If concentration is broken, it is unable to perform it's Concentration Turn, and gains 1 Vulnerability Stack.

Move Turn (Initiative 13) - Thunder Step: This creature teleports 60ft away with a Thunderous Boom. Each creature within 10 feet of the Lightning Primal must make a Constitution saving throw (DC 15), taking 3d10 thunder damage on a failed saving throw, or half as much damage on a successful one.  A target in melee may attempt to goad the Lightning Elemental as a Standard Action. This will cause the Lightning Primal to attack with a Slam to the melee creature instead on their Move Turn.  Attacks of Opportunity are permitted - at a disadvantage - unless the user has the Sentinel Feat.

Action Turn (Initiative 6) - Thunderous Roundabout : Lightning Primal will ether use their multiattack of 2 Slams if in melee range with a target, or will cast Lightning Bolt if no targets are in range or if it has attacked with a multiattack in the previous round.

Conjure Turn (Initiative 1) - Lightning Simulacrum : Lightning Primal Spawns a Lightning Similicrum. This Similicrum has hit points equal to half of the Lightning Elemental's current hit points.  If a creature ends their turn within the Lightning Primal's space, the summoned effect does not go off. Instead, creatures within the space must succeed at a Constitution Saving Throw at a disadvantage (DC 15) - being dealt 3d10 Lightning Damage on a failed saving throw, or half as much damage on a successful one.

Multiattack : Lightning Elemental hits twice with slam.

Slam : +9, (2d8+5) bludgeoning damage

Call Lightning: 60ft range - Each creature within 5 feet of that point must make a Dexterity saving throw (DC 15). A creature takes 3d10 lightning damage on a failed save, or half as much damage on a successful one.

Lightning Bolt : A stroke of lightning forming a line 100 feet long and 5 feet wide blasts out from you in a direction you choose. Each creature in the line must make a Dexterity saving throw (DC 15). A creature takes 8d6 lightning damage on a failed save, or half as much damage on a successful one. The lightning ignites flammable objects in the area that aren't being worn or carried.

The combat so far has been very good!  You can explain to your players how these abilities work, or do a sort of skill check (in Io, we use Scan Checks) to learn more about abilities as they pop up with the creature.