Elthunder

When you cast the spell, choose a point you can see within range. A bolt of lightning flashes down from the sky to that point. Each creature within 5 feet of that point must make a Dexterity saving throw. A creature takes 1d12 lightning damage on a failed save, or half as much damage on a successful one. The Dexterity saving throw is made with disadvantage if the target is wearing metal armor. 

If you are outdoors in stormy conditions when you cast this spell, the spell gives you control over the existing storm instead of creating a new one. Under such conditions, the spell’s damage increases by 1d12. The spell's damage increases by 1d12 when you reach 5th level (2d12), 11th level (3d12), and 17th level (4d12).

It acts as the second "stage" of the hierarchy of thunder magic, as a counterpart to Elfire and Elwind; it is superior to the basic Thunder tome but requires a higher weapon level to use, and in turn it is surpassed by the more advanced and powerful Arcthunder and Thoron tomes. This spell is from the Fire Emblem franchise.