The Last Stand Spell would prevent any troops inside it form dying. They would instead be left with one health. And in order to make it less op 1/4 of all the troops affected by the spell's health will be taken away (when it ends or when they leave the spell range). Now some statistics.

Cost: 25,000 +2,500 per level
Affect length: 5 seconds +2, 2, 3, 3 will add up to fifteen total
Affect range: seven or whatever the other spells range is.
Upgrade cost: 500,000 , 1,500,000 , 2,500,000 , 4,000,000

It will look green or orange and have either a leaf or some spirally things in it. It would be unlockable at spell factory six (it could be four, but then some stuff would have to be moved around).