Frodo Baggins

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

Kyler, Sigardian Emissary

Whenever another Human you control enters, put a +1/+1 counter on Kyler.
Other Humans you control get +1/+1 for each counter on Kyler.

Ayara, First of Locthwain

Whenever Ayara or another black creature you control enters, each opponent loses 1 life and you gain 1 life.
{T}, Sacrifice another black creature: Draw a card.

Ayula, Queen Among Bears

Whenever another Bear you control enters, choose one —
• Put two +1/+1 counters on target Bear.
• Target Bear you control fights target creature you don't control.

Arahbo, the First Fang

Other Cats you control get +1/+1.
Whenever Arahbo or another nontoken Cat you control enters, create a 1/1 white Cat creature token.

Zhao Zilong, Tiger General

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)
Whenever Zhao Zilong blocks, it gets +1/+1 until end of turn.

Inalla, Archmage Ritualist

Eminence — Whenever another nontoken Wizard you control enters, if Inalla is in the command zone or on the battlefield, you may pay {1}. If you do, create a token that's a copy of that Wizard. The token gains haste. Exile it at the beginning of the next end step.
Tap five untapped Wizards you control: Target player loses 7 life.

Gylwain, Casting Director

Whenever Gylwain or another nontoken creature you control enters, choose one —
• Create a Royal Role token attached to that creature.
• Create a Sorcerer Role token attached to that creature.
• Create a Monster Role token attached to that creature.

Marwyn, the Nurturer

Whenever another Elf you control enters, put a +1/+1 counter on Marwyn.
{T}: Add an amount of {G} equal to Marwyn's power.

Blue, Loyal Raptor

Partner with Owen Grady, Raptor Trainer (When this creature enters, target player may put Owen into their hand from their library, then shuffle.)
For each kind of counter on Blue, Loyal Raptor, each other Dinosaur you control enters with a counter of that kind on it.

Clement, the Worrywort

Vigilance
Whenever Clement or another creature you control enters, return up to one target creature you control with lesser mana value to its owner's hand.
Frogs you control have "{T}: Add {G} or {U}. Spend this mana only to cast a creature spell."

Black Panther, Wakandan King

First strike
Survey the Realm — Whenever Black Panther or another creature you control enters, put a +1/+1 counter on target land you control.
Mine Vibranium — {3}: Move all +1/+1 counters from target land you control onto target creature. If one or more +1/+1 counters are moved this way, you gain that much life and draw a card.

Shelinda, Yevon Acolyte

Lifelink
Whenever another creature you control enters, put a +1/+1 counter on that creature if its power is less than Shelinda's power. Otherwise, put a +1/+1 counter on Shelinda.

Cadric, Soul Kindler

The "legend rule" doesn't apply to tokens you control.
Whenever another nontoken legendary permanent you control enters, you may pay {1}. If you do, create a token that's a copy of it. That token gains haste. Sacrifice it at the beginning of the next end step.

Calix, Guided by Fate

Constellation — Whenever Calix or another enchantment you control enters, put a +1/+1 counter on target creature.
Whenever Calix or an enchanted creature you control deals combat damage to a player, you may create a token that's a copy of a nonlegendary enchantment you control. Do this only once each turn.

Arwen, Weaver of Hope

Each other creature you control enters with a number of additional +1/+1 counters on it equal to Arwen's toughness.

Denry Klin, Editor in Chief

Denry Klin enters with your choice of a +1/+1, first strike, or vigilance counter on it.
Whenever a nontoken creature you control enters, if Denry Klin has counters on it, put the same number of each kind of counter on that creature.

Elrond, Lord of Rivendell

Whenever Elrond or another creature you control enters, scry 1. If this is the second time this ability has resolved this turn, the Ring tempts you.

Elas il-Kor, Sadistic Pilgrim

Deathtouch
Whenever another creature you control enters, you gain 1 life.
Whenever another creature you control dies, each opponent loses 1 life.

Kamiz, Obscura Oculus

Whenever you attack, target attacking creature can't be blocked this turn. It connives. Then choose another attacking creature with lesser power. That creature gains double strike until end of turn. (To have a creature connive, draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on that creature.)