"Few have ever come hither through greater peril or on an errand more urgent."
—Elrond

Frodo Baggins

Whenever Frodo Baggins or another legendary creature you control enters, the Ring tempts you.
As long as Frodo is your Ring-bearer, it must be blocked if able.

The Lord of the Rings: Tales of Middle-earth

Whenever Frodo Baggins or another legendary creature enters the battlefield under your control, the Ring tempts you.
As long as Frodo is your Ring-bearer, it must be blocked if able.

As the Ring tempts you, you get an emblem named The Ring if you don't have one. Then your emblem gains its next ability and you choose a creature you control to become (or remain) your Ring-bearer.

Each player can have only one emblem named The Ring and only one Ring-bearer at a time.

Each time the Ring tempts you, you must choose a creature if you control one.

If Frodo Baggins is your Ring-bearer but each creature the defending player controls can't block for any reason (such as by having greater power than Frodo along with the first ability of the Ring emblem), then Frodo Baggins isn't blocked. If there's a cost associated with blocking Frodo Baggins, the defending player isn't forced to pay that cost, so it doesn't have to be blocked in that case either.

If Frodo Baggins is your Ring-bearer, only one creature is required to block it. Other creatures may also block it and are free to block other creatures or not block at all.

If the creature you choose as your Ring-bearer was already your Ring-bearer, that still counts as choosing that creature as your Ring-bearer for the purpose of abilities that trigger "whenever you choose a creature as your Ring-bearer" or abilities that care about which creature was chosen as your Ring-bearer.

Some spells and abilities that cause the Ring to tempt you may require targets. If each target chosen is an illegal target as that spell or ability tries to resolve, it won't resolve. The Ring won't tempt you.

The Ring can tempt you even if you don't control a creature. In this case, abilities that trigger "whenever the Ring tempts you" will still trigger.

The Ring gains its abilities in order from top to bottom. Once it gains an ability, it has that ability for the rest of the game.