Thundurus (5e Creature)
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Medium elemental (shapechanger), neutral
Skills Arcana +10, History +10, Nature +10
Shapechanger. While Thundurus holds the item 'Reveal Glass' it can use a bonus action to polymorph into it's large sized Therian form, or back into its true Incarnate form. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. Thundurus remains in the form it takes even upon death.
Prankster (Incarnate Form Only). Thundurus has a +5 bonus to initiative checks.
Defiant (Incarnate Form Only). When Thundurus is forced to roll disadvantage on a saving throw or attack roll it makes, which is caused by a hostile creature's spell or ability, its next melee weapon attack it makes has a +5 bonus to its attack and damage rolls.
Volt Absorb (Therian Form Only). Whenever Thundurus is subjected to lightning damage, it takes no damage and regains a number of hit points equal to the lightning damage dealt.
Force Of Nature. Thundurus can cast the 'Control Weather' spell at will.
Multiattack. Thundurus makes 2 hammer arm attacks.
Hammer Arm (Incarnate Form Only). Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 18 (4d6 + 4) bludgeoning damage and Tornadus's movement speed is reduced by 10 until the end of its next turn.
Volt Switch. Melee Spell Attack: +12 to hit, reach 30 ft., one target. Hit: 20 (4d6 + 6) lightning damage and thunderous moves up to its flying speed away from its target without provoking opportunity attacks.
Thunder. Ranged Spell Attack: +12 to hit, range 90 ft., one target. Hit: (4d10 + 6) lightning damage plus 28 (2d10) thunder damage.
Wildbolt Storm (Recharge 5-6). Thundurus causes lightning and wind to lash around it in a 30 foot radius, forcing each creature in the area other than Thundurus to make a DC 20 constitution saving throw, taking 21 (6d6) bludgeoning damage, 21 (6d6) lightning damage, and gaining the paralyzed condition for the next minute, being able to repeat the saving throw at the end of each of their turns. On a success a creature takes half as much damage and isn't paralyzed.
The can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The regains spent legendary actions at the start of its turn.
Detect. Thundurus makes a Wisdom (Perception) check.
Charge (Costs 3 Actions). Thundurus makes a DC 20 constitution check. On a success, the next time it makes a saving throw it rolls a d4 and adds it to the roll and the next time it deals lightning damage, it rolls maximum damage.