Singer of Swift Rivers

Flash
When this creature enters, put a shield counter on another target creature you control. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)
You may cast Merfolk spells as though they had flash.

Swooping Protector

Flash
Flying
This creature enters with a shield counter on it. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)

Contractual Safeguard

Addendum — If you cast this spell during your main phase, put a shield counter on a creature you control. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)
Choose a kind of counter on a creature you control. Put a counter of that kind on each other creature you control.

Protection Magic

Put a shield counter on each of up to three target creatures. (If a creature with a shield counter would be dealt damage or destroyed, remove a shield counter from it instead.)

Undercover Operative

You may have this creature enter as a copy of any creature on the battlefield, except it enters with a shield counter on it if you control that creature. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)

Rhox Pummeler

This creature enters with a shield counter on it. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)
This creature has trample as long as it has a shield counter on it.

Sanctuary Warden

Flying
This creature enters with two shield counters on it.
Whenever this creature enters or attacks, you may remove a counter from a creature or planeswalker you control. If you do, draw a card and create a 1/1 green and white Citizen creature token.

Dapper Shieldmate

This creature enters with a shield counter on it. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)
During your turn, this creature gets +2/+0.

Elspeth Resplendent

+1: Choose up to one target creature. Put a +1/+1 counter and a counter from among flying, first strike, lifelink, or vigilance on it.
−3: Look at the top seven cards of your library. You may put a permanent card with mana value 3 or less from among them onto the battlefield with a shield counter on it. Put the rest on the bottom of your library in a random order.
−7: Create five 3/3 white Angel creature tokens with flying.

Brotherhood Outcast

When this creature enters, choose one —
• Return target Aura or Equipment card with mana value 3 or less from your graveyard to the battlefield.
• Put a shield counter on target creature. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)

Summon: Magus Sisters

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II, III — Choose one at random —
• Combine Powers! — Put three +1/+1 counters on target creature.
• Defense! — Put a shield counter on target creature. You gain 3 life.
• Fight! — This creature fights up to one target creature an opponent controls.
Haste

Falco Spara, Pactweaver

Flying, trample
Falco Spara enters with a shield counter on it.
You may look at the top card of your library any time.
You may cast spells from the top of your library by removing a counter from a creature you control in addition to paying their other costs.

Brokers Veteran

When this creature dies, put a shield counter on target creature you control. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)

Perrie, the Pulverizer

When Perrie enters, put a shield counter on target creature. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)
Whenever Perrie attacks, target creature you control gains trample and gets +X/+X until end of turn, where X is the number of different kinds of counters among permanents you control.

Family's Favor

Whenever you attack, put a shield counter on target attacking creature. Until end of turn, it gains "Whenever this creature deals combat damage to a player, remove a shield counter from it. If you do, draw a card." (If a creature with a shield counter on it would be dealt damage or destroyed, remove a shield counter from it instead.)

Disciplined Duelist

Double strike
This creature enters with a shield counter on it. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)

Titan of Industry

Reach, trample
When this creature enters, choose two —
• Destroy target artifact or enchantment.
• Target player gains 5 life.
• Create a 4/4 green Rhino Warrior creature token.
• Put a shield counter on a creature you control.

Boon of Safety

Put a shield counter on target creature. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)
Scry 1.

Agent's Toolkit

This artifact enters with a +1/+1 counter, a flying counter, a deathtouch counter, and a shield counter on it. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)
Whenever a creature you control enters, you may move a counter from this artifact onto that creature.
{2}, Sacrifice this artifact: Draw a card.

Voice of the Vermin

This creature enters with a shield counter on it. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)
Whenever this creature attacks, target creature you control has base power and toughness 4/4 until end of turn.