The massive, dog-faced elk charges into battle, lightning crackling between its hooves and antlers, as its giant rider throws bolts of lightning.

The sight of a storm giant charging to battle atop a baying thrummren is both breathtaking and terrifying.

Heavenly Wanderers. Herds of thrummrens migrate from mountain range to mountain range across vast regions of the

Upper Planes. As they travel en masse, storm clouds gather above them, and the pounding of their hooves against the ground is akin to thunder. The lightning storms generated by their proximity are truly amazing to behold.

Giant Bond. Most thrummrens on the Material Plane serve as the mounts of storm giant cavaliers. The relationship between mount and rider is complex, with control of the pairing seeming to pass from one to the other and back. Thrummrens never abandon their riders, defending riders to the death if necessary. If its rider falls in battle, a thrummren continues its assault until all foes have fallen. The thrummren then returns the rider’s body to its home community, regardless of the distance.

Simurg Friends. When they encounter each other on the forested mountainsides they prefer, thrummren and simurgs share information. The two creatures often converse while on the move with the simurg perched atop the thrummren, looking to observers like some kind of chimeric creature with a long-feathered tail streaming behind it.

Thrummren

Gargantuan celestial, chaotic good
Armor Class 17 (natural armor)
Hit Points 198 (12d20 + 72)
Speed 60 ft.

STR	DEX	CON	INT	WIS	CHA
21 (+5)	19 (+4)	22 (+6)	10 (+0)	15 (+2)	10 (+0)

Saving Throws Dex +8, Wis +6, Cha +4
Damage Resistances cold, thunder
Damage Immunities lightning, poison
Condition Immunities poisoned
Senses darkvision 120 ft., passive Perception 12
Languages Common, Giant, telepathy 60 ft.
Challenge 12 (8,400 XP)

Lightning Absorption. Whenever the thrummren is subjected to lightning damage, it takes no damage and instead regains a number of hp equal to the lightning damage dealt.

Magic Resistance. The thrummren has advantage on saving throws against spells and other magical effects.

Magic Weapons. The thrummren’s weapon attacks are magical.

Storm Hide. A creature that touches the thrummren or hits it with a melee attack while within 5 feet of it takes 7 (2d6) lightning damage. The thrummren can choose for its rider to not be affected by this trait.

Actions

Multiattack. The thrummren makes two attacks: one with its gore and one with its hooves.

Gore. Melee Weapon Attack: +9 to hit, reach 15 ft., one target. Hit: 24 (3d12 + 5) piercing damage plus 10 (3d6) lightning damage.

Hooves. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 14 (2d8 + 5) bludgeoning damage plus 10 (3d6) thunder damage.

Thunder Stomp (Recharge 5-6). The thrummren rears back and slams its front hooves into the ground. Each creature within 20 feet of the thrummren must make a DC 17 Strength saving throw. On a failure, a creature takes 35 (10d6) thunder damage, is pushed up to 10 feet away from the thrummren, and is deafened until the end of its next turn. On a success, a creature takes half the damage and isn’t pushed or deafened.

Reactions

Protect Rider. When the thrummren’s rider is the target of an attack the thrummren can see, the thrummren can choose to become the target of the attack instead.