Artemis/Parvati will give you 3x hp and atk for all your green monsters. Use the dark golem, not the earth guardian and you should be fine on Master. Just remember to have Artemis's skill charged up for rounds 5 and 10, and the dark golem charged up for round 10.
Artemis : x2 HP
Parv : x1.5 HP
Should be fine
Ok, well I shall give this a try. I will add the dark golem and build up my skills as you guys suggest. This shall be interesting!
EDIT: Ok wait. I have an unevolved Artemis, so I do not get the HP from her.