Nominally, there are multiple ways the gate interaction can go.
1: You touch the gate without the crests, the Priest Spawns. Lose to the Priest (The most likely outcome.) You get a parasite stack, and are left in the shack. When you escape, you will need to backtrack through the mutated village to collect the crests from chests, before returning to unlock the gate.
2: You touch the gate w/o the crests, Priest Spawns. However, you are a gigachad 1% player who can use uparrow to instantly fire an arrow into his face after baiting him into making an attack (and thus no barrier for that brief moment). You fill his face with enough arrows such that he dies, and get both pieces instantly without the need to backtrack.
3: You've cleared the area once, and gotten the explosive arrow magic. Just blow up his barrier and defeat him. He still drops the crests.
The fight isn't unwinnable on the first go, it just requires stupendous (and i mean STUPENDOUS) amounts of skill.