Hello everyone.

I have been working on creating a Nordic themed magic system for my BBEG, and im having a bit of trouble coming up with new spells. The reason being that i would like most of the spells to have 2 round casting times (or more).

The villain is rich and has acces to loads of minions to protect him while he casts.

Does anyone have any ideas on how to balance a spell that requires 2 rounds of concentration to cast? 

Ideas for Nordic themed spells would also be highly appreciated :)

Fury of Thor
2nd Level, Evocation, Spell
Casting Time: 1 action
Duration: 2 rounds, Concentration
Range: Special, see description
Components: V, S
Description:

This spell has two stages, depending on whether you were already concentrating on this spell while casting it: a Charge stage and a Release stage.

Charge Stage: If you are not concentrating on this spell when you cast it the spell is cast in the Charge stage upon yourself. You gain an aura of lightning until the spell ends: when a creature moves to be within 5 ft of you for the first time on a turn or starts its turn within 5 ft of you it takes lightning damage equal to your spellcasting ability modifier. Any creature that hits you with a melee attack also receives this damage. You can cast this spell again while concentrating on it to have it be cast at the Release stage.The spell ends at the end of your next turn.

Release Stage: If you cast this spell while already concentrating on it in the Charge Stage then you now cast it at the Release stage: Choose one creature you can see within range - that creature must make a Dexterity saving throw as the lightning you have charged is released in a violent bolt. If the target fails the saving throw it takes 4d12 lightning damage or half this on success. Creatures that are made of metal or wear a lot of metal have disadvantage on this saving thow. After this the spell, in both stages, end.

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Northern Winds
1st Level, Evocation, Spell
Casting Time: 1 actions
Duration: 2 rounds, Concentration
Range: Self
Components: V, S
Description:

You bring forth the icy winds of the northern tundra to hamper your foe. When you cast this spell the cold and snowy winds encircle you, harmlessly, as you charge the air with your magic. On your next turn you may use your action to target one creature you can see within 90 ft of you, causing the cold winds to assail it. That creature must make a Constitution saving throw and if it fails its speed is halved, and it has disadvantage to all attack rolls. These effects last until the end of its next turn. If it succeeds the saving throw its speed is slowed by 10 ft until the end of its next turn. This spell ends at the end of your next turn after casting the spell although any effects placed upon a creature remain as stated.

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Couple of ideas, untested, unsure if balanced, never gone into the "2 turn" thing as the game wasn't really based around them. Also, don't find much inspiration in Nordic themes, to be honest. The casting times is odd, as there is no precedent for it so it is hard to describe/put in place. Easier to have it be "1 action" but with text to indicate using the effect on a subsequent turn, and with it being concentration, it achieves everything mechanically without having to go into complication of what "Casting Time; 2 actions" means. Anyway, hopefully gets the ball rolling for you.

Thanks for the ideas, they are really good! This pretty much serves the same purpose, and its a good way to achive what i want.