New epic spell: invisibility potion

Name: Invisibility potion
Training cost: 30.000 elixir
Target: Attacker's troops
Effect type: whole the troops who enter in its area become invisible for five seconds
Training time: 45 minutes
Description: When your troops are invisible you're enemy's defenses can't attack them
I hope you like this potion
Sorry for my bad english ;)

Ten seconds is a long time. Too long.

Adding this potion takes away from the queen. She is able to cloak herself after level 5 so making it into a potion overpowers everyone while taking away from her awesome ability. That doesn't make sense. Leave the op spells for just the heroes.

Its op. Really OP.