Sméagol, Helpful Guide

At the beginning of your end step, if a creature died under your control this turn, the Ring tempts you.
Whenever the Ring tempts you, target opponent reveals cards from the top of their library until they reveal a land card. Put that card onto the battlefield tapped under your control and the rest into their graveyard.

The Black Breath

Creatures your opponents control get -1/-1 until end of turn. The Ring tempts you.

Gollum, Patient Plotter

When Gollum leaves the battlefield, the Ring tempts you.
{B}, Sacrifice a creature: Return this card from your graveyard to your hand. Activate only as a sorcery.

Dúnedain Rangers

Landfall — Whenever a land you control enters, if you don't control a Ring-bearer, the Ring tempts you.

One Ring to Rule Them All

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — The Ring tempts you, then each player mills cards equal to your Ring-bearer's power.
II — Destroy all nonlegendary creatures.
III — Each opponent loses 1 life for each creature card in that player's graveyard.

Tainted Wood

{T}: Add {C}.
{T}: Add {B} or {G}. Activate only if you control a Swamp.

Llanowar Wastes

{T}: Add {C}.
{T}: Add {B} or {G}. This land deals 1 damage to you.

Call of the Ring

At the beginning of your upkeep, the Ring tempts you.
Whenever you choose a creature as your Ring-bearer, you may pay 2 life. If you do, draw a card.

Enraged Huorn

Trample
When this creature enters, the Ring tempts you.

Viscera Seer

Sacrifice a creature: Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Claim the Precious

Destroy target creature. The Ring tempts you.

Uruk-hai Berserker

When this creature enters, the Ring tempts you.

Deathcap Glade

This land enters tapped unless you control two or more other lands.
{T}: Add {B} or {G}.

Woodland Cemetery

This land enters tapped unless you control a Swamp or a Forest.
{T}: Add {B} or {G}.

Swamp

Golgari Rot Farm

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {B}{G}.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Witch-king of Angmar

Flying
Whenever one or more creatures deal combat damage to you, each opponent sacrifices a creature of their choice that dealt combat damage to you this turn. The Ring tempts you.
Discard a card: Witch-king of Angmar gains indestructible until end of turn. Tap it.

Sam's Desperate Rescue

Return target creature card from your graveyard to your hand. The Ring tempts you.

Twilight Mire

{T}: Add {C}.
{B/G}, {T}: Add {B}{B}, {B}{G}, or {G}{G}.

Inherited Envelope

When this artifact enters, the Ring tempts you.
{T}: Add one mana of any color.

Bombadil's Song

Target creature you control gets +1/+1 and gains hexproof until end of turn. The Ring tempts you. (A creature with hexproof can't be the target of spells or abilities your opponents control.)