The Master Ring is an... interesting card.

It says "cancel effects" of an encounter card so that includes Doom/Surge correct?

Also, can you get instant guarded cards with it? For instance, I play Mithril Shirt and attach a location to it. I then use the Master Ring to cancel all effects and discard the location which frees up the Mithril Shirt and I attach it to one of my characters. I then finish resolving Master Ring and draw the next encounter card, be it enemy, location, or treachery. All good?

7 minutes ago, RogueSeventeen said:

The Master Ring is an... interesting card.

It says "cancel effects" of an encounter card so that includes Doom/Surge correct?

Also, can you get instant guarded cards with it? For instance, I play Mithril Shirt and attach a location to it. I then use the Master Ring to cancel all effects and discard the location which frees up the Mithril Shirt and I attach it to one of my characters. I then finish resolving Master Ring and draw the next encounter card, be it enemy, location, or treachery. All good?

You are correct that it includes Doomed and Surge.

However, you cannot use it to get instant guarded player cards. The Guarded X keyword does not reveal encounter cards - you are instructed to discard from the deck until you find a card of the right kind and then attach it.

Interesting, so the When Revealed effects of enemies or locations attached to guarded cards do no resolve.

1 hour ago, RogueSeventeen said:

Interesting, so the When Revealed effects of enemies or locations attached to guarded cards do no resolve.

One of the benefits of using guarded cards, if you can afford the added threat to staging. You can avoid really bad enemy reveals/surges this way.