Crab Umbra

Enchant creature
{2}{U}: Untap enchanted creature.
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Thassa's Ire

{3}{U}: You may tap or untap target creature.

Triton Tactics

Up to two target creatures each get +0/+3 until end of turn. Untap those creatures. At this turn's next end of combat, tap each creature that was blocked by one of those creatures this turn and it doesn't untap during its controller's next untap step.

Chakram Retriever

Partner with Chakram Slinger (When this creature enters, target player may put Chakram Slinger into their hand from their library, then shuffle.)
Whenever you cast a spell during your turn, untap target creature.

Unstoppable Plan

At the beginning of your end step, untap all nonland permanents you control.

Aphetto Alchemist

{T}: Untap target artifact or creature.
Morph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Sokrates, Athenian Teacher

Defender
Sokrates has hexproof as long as it's untapped.
Sokratic Dialogue — {T}: Until end of turn, target creature gains "If this creature would deal combat damage to a player, prevent that damage. This creature's controller and that player each draw half that many cards, rounded down."

Act of Heroism

Untap target creature. It gets +2/+2 until end of turn and can block an additional creature this turn.

Captain of the Mists

Whenever another Human you control enters, untap this creature.
{1}{U}, {T}: You may tap or untap target permanent.

Veteran's Reflexes

Target creature gets +1/+1 until end of turn. Untap that creature.

Vizier of Tumbling Sands

{T}: Untap another target permanent.
Cycling {1}{U} ({1}{U}, Discard this card: Draw a card.)
When you cycle this card, untap target permanent.

Acrobatic Leap

Target creature gets +1/+3 and gains flying until end of turn. Untap it.

Teardrop Kami

Sacrifice this creature: You may tap or untap target creature.

Shore Up

Target creature you control gets +1/+1 and gains hexproof until end of turn. Untap it. (It can't be the target of spells or abilities your opponents control.)

Alarum

Untap target nonattacking creature. It gets +1/+3 until end of turn.

Call to Glory

Untap all creatures you control. Samurai creatures you control get +1/+1 until end of turn.

Twiddle

You may tap or untap target artifact, creature, or land.

Aura of Dominion

Enchant creature
{1}, Tap an untapped creature you control: Untap enchanted creature.

Rustler Rampage

Spree (Choose one or more additional costs.)
+ {1} — Untap all creatures target player controls.
+ {1} — Target creature gains double strike until end of turn.

Light the Way

Choose one —
• Put a +1/+1 counter on target creature or Vehicle. Untap it.
• Return target permanent you control to its owner's hand.

Djeru's Resolve

Untap target creature. Prevent all damage that would be dealt to it this turn.
Cycling {2} ({2}, Discard this card: Draw a card.)

Cerulean Wisps

Target creature becomes blue until end of turn. Untap that creature.
Draw a card.

Breaching Hippocamp

Flash (You may cast this spell any time you could cast an instant.)
When this creature enters, untap another target creature you control.

Magic Damper

Target creature you control gets +1/+1 and gains hexproof until end of turn. Untap it.

Maze of Ith

{T}: Untap target attacking creature. Prevent all combat damage that would be dealt to and dealt by that creature this turn.

Vault Skyward

Target creature gains flying until end of turn. Untap it.

Blessed Alliance

Escalate {2} (Pay this cost for each mode chosen beyond the first.)
Choose one or more —
• Target player gains 4 life.
• Untap up to two target creatures.
• Target opponent sacrifices an attacking creature of their choice.

Meekstone

Creatures with power 3 or greater don't untap during their controllers' untap steps.