The Shield Spell:

Appearance:
Red and when deployed a red ring as small as the heal spell shows.
Stats:
-The spell ring is as small as the heal spell.
-All troops inside the ring are protected if there is still HP in the spell.
-It can protect troops from 200 damage, 300, 400 ,and so on.
-When the spell can't defend troops anymore, the red ring disappears signalling that your troops inside can take damage now.
-The spell targets all troops.

Strategies: Protect your balloons from air bombs and splash damage that can take them out quickly.
You can protect a horde of troops that are near death.
Protect your tanks so they can live on longer and create a longer distraction for other troops to do work.
Protect your troops from CC troops that do large damage such as wizards.

I would like some feedback about this idea, and if there is another spell like this one or if this unbalances the game.
Thanks for reading.