Invisibilty Potion

Now: Don't go thinking, 'Oh, nope, another immortality spell', I've had some newer ideas.

Name of Spell:Invisibility Potion
Training Cost (usually in gold): 17,000 gold for level 1.
Targets: Your troops.
Effect Type: Well... can someone post the "Types" in the comments so I can adjust this?
Damage Type/Amount (if applicable): Irrelevant
Training Time: 30 Minutes (duh).
Description: Well, it makes your troops invisible in a 10x10 circle, except for wizard towers, archer towers, and any other towers that actually have a human connected to them. Like, a Barbarian King.
Research/Spell Levels: Levels *, **, and ***.
Lab Level: Level**: Lab 3, Level***: Lab 5.

Let's get into detail here...

LEVEL 1
Invisibility for 5 secs.
Costs 17,000.
Spell Factory Level 6.

LEVEL 2
Invisibility for 10 secsCosts 18,500.
Lab Level 3

Level 3
Invisibility for 15 secs.
Cost 20,000.
Lab Level 5

Is there anything that I should go into more detail for? Thanks :)

Masoncat