After more than five years since this card's publication, how can there still be no reviews of The One Ring, the centerpiece item of the Lord of the Rings?
This card certainly isn't an auto-include for deck building, but is very good in the right deck. Even at its simplest use, you get to reduce your deck size by one (since the ring starts in play) and pull another card from your deck during setup, giving you effectively seven starting cards and a deck size of 48 instead of 50. Depending on what your deck needs, all four of the master attachments are potentially useful: Power of Command boosts willpower, Inner Strength for blocking, Strength and Courage for attacking, or Well Preserved for health.
It is of course dangerous to use this in a high threat deck or on a quest where there are severe threat conditions, but for a low threat deck (like hobbits, a very thematic choice, or The Grey Wanderer) the threat penalty probably won't even be noticed.
I like the threat payment abilities on the attachments because you're already getting benefit even without paying. I wish the actions had a similar format where you had a base effect with no threat cost and an optional threat cost to boost the power. For example, The Master Ring could have its effect plus an optional threat payment to not draw a replacement card. Similarly, The Ring of Power could have a stat boost and optional threat payment to ready the hero. Likewise, The Ruling Ring could have one target by default plus an optional threat payment for an extra target. In all three cases, the base cost and threat cost would need to be balanced to the effects granted.
Example decks: