“Emissary of the Oasis”’ last sentence applies even when your opponent attacks with a Level 3 or lower Normal Monster; the Battle Damage to you becomes zero.
If you have “Emissary of the Oasis” with “Raregold Armor”, and a Level 3 or lower Normal Monster, your opponent cannot attack.
A Monster Token is a Normal Monster, but a Ritual Monster without an effect is not a Normal Monster.