Mirage Spell - New Spell

I guess I just need a clarification.

Is this spell going to be used to help increase your offensive power by adding more troops to the field for a limited time and do damage? Or is the spell for distracting defenses to protect your own troops for a limited time?

I like the former idea, the latter sounds a bit useless. If we already have a heal spell, we don't need extra troops to take damage or distract defenses when we can just heal the ones we already have.

If you have a mirage troop, I think it would make sense for them to be almost like ghosts. They cannot be attacked (therefore do not have HP), but they can hurt defenses (at a weaker DPS, like you stated). They will still only last for a short amount of time, but the spell can be used to double your offenses in a small area in order to take out some buildings quicker or focus your attacks on high hit-point buildings.