Crystalline Frost Goblin

Nimble Escape. The goblin can take the Disengage or Hide action as a bonus action on each of its turns.

Crystal absorption. Because of the to big crystal formations around their arms they can capture some of the incoming energy, lessening its effect on it and storing it for their next melee attack. They have resistance to the triggering damage type until the start of their next turn.

Slam. Melee Attack: +5; to hit, reach 10 ft., one target. Hit: 8, 1d10+3, Bludgeoning damage. If they have energy stored in their crystal arms they do an extra 1d8 damage of the corresponding element. If there is more than one element absorbed, this only uses one of them.

Ground Pound. The Crystalline Juggernaut can try to slam the ground releasing all the stored up energy in the crystals, causing every one in a 5 ft radius to take a d6 of each element stored in the crystals,

they also have to do a DC 13 dexterity saving throw or be knocked prone.

Lunge attack. The Crystalline Juggernaut Lunges forward their full movement, doing 1d10 bludgeoning damage along the way. If they have energy stored in their crystal, anyone in their way will take 1d8 damage of the corresponding type.