Do I also have to pay one water if there is nothing in an oasis?
Realm of the Desert Sons
No. Only oases with symbols can be rated, and water must only be paid for oases that can be rated.
If two oases are completed at the same time, may I take water from one of the oases and apply it to use the highest Influence Stone in the other oasis?
Realm of the Desert Sons
No. If two oases are discovered simultaneously, you first have to pay one water for each of the two highest Influence Stones.