Good question. Kram and Legolas are right, but
since I typed everything out already since this is a detailed question, let's look at the why. The question is which one is activated first, and so we need the abilities:
Abomination of Desolation: If used by a Greek, place in opponent's territory. Each time opponent draws cards (except during draw phase), you may discard a card in that territory except a Lost Soul.
Hidden Treasures: Once per turn, if your lone green brigade prophet begins a battle, you may play an Enhancement or discard an evil Enhancement in an opponent's deck.
Now, Abomb goes off on the draw. However, Hidden Treasures triggers once you begin the battle, as we know from other HT rulings (it looks to see who starts the battle and who finishes the battle, determining the entire time whether the condition is met).
So we see that HT 'triggers' first, the instant that Isaiah enters battle, and is waiting for everything to resolve from him being placed in battle to determine if it can go off. Abomb only goes off once Isaiah's abilities start resolving, and thus is 'triggered' second and will have to wait until HT has completed.
