Hypervigiilance
Enchantment - Aura
Enchant Creature
Enchanted creature can't be tapped. (If attacking would cause it to tap, it can't attack.)

Some morbid cards!

Missing Person
Instant
Return target creature to its owner's hand.
Morbid - If a creature died this turn, put the creature on top of its owner's library instead.
When Franz's father went missing, he thought he'd be back any day. When the bodies started showing up, he began to have doubts.

Maddening Grief
Sorcery
Target player discards two cards.
Morbid - If a creature died this turn, that player discards two cards at random instead.

Avenging Rampage
Sorcery
Untap target creature and gain control of it until end of turn. It gains haste.
Morbid - If a creature died this turn, you may cast ~ as though it had flash.

Fertilize
Instant
Search your library for a basic land card, put it onto the battlefield tapped, then shuffle your library.
Morbid - If a creature died this turn, search your library for up to two basic land cards this way instead of one.

Babywalkers! (low cmc)

Baby Nissa
Legendary Planeswalker - Nissa
{+1} Untap target land you control. Until your next turn, you may have that land become a 2/4 Green Elemental creature with haste, vigilance, and reach.
{-2} Search your library for a basic land card, put it onto the battlefield tapped, then shuffle your library.
{-7} You get an emblem with "whenever a creature you control attacks or blocks, put two +1/+1 counters on it".
{3}

Baby Elspeth
Legendary Planeswalker - Elspeth
{+1} Up to one target creature gets +1/+1 and gains flying and vigilance until your next turn.
{-2} Create two 1/1 white soldier creature tokens
{-7} Create seven 1/1 white soldier creature tokens, then destroy all creatures with power 3 or greater.
{3}

Baby Liliana
Legendary Planeswalker - Liliana
{+1} Choose up to one target creature. When that creature dies before the beginning of your next upkeep, exile it and create a tapped 2/2 black zombie creature token.
{-2} Return target creature card from your graveyard to your hand. The next creature spell you cast with that name this turn enters the battlefield with a +1/+1 counter on it.
{-6} Put each creature card exiled with ~ onto the battlefield under your control.
{3}

Baby Jace
Legendary Planeswalker - Jace
{+1} The next time a creature you control deals combat damage to a player this turn, draw a card.
{-1} Tap target creature. It doesn't untap during its controller's next untap step.
{-6} Put three target permanents on top of their owners' libraries.
{2}

Baby Chandra
Legendary Planeswalker - Chandra
{+2} Each player exiles the top card of their library, and may play that card until the end of their next turn.
{-2} Create a 3/1 red elemental creature token with trample and haste. Sacrifice it at the beginning of your next end step.
{-12} ~ deals 10 damage to target creature or player.
{4}

Some mill cards!

Lochdown
Instant
Target spell's controller puts the top card of their library into their graveyard. Then, counter that spell unless its controller pays for each card in their graveyard.

Grist for the Mill
Instant
Target creature's controller puts the top card of their library into their graveyard. Until end of turn that creature loses all abilities and gets -X/-X, where X is the number of cards in its controller's graveyard.

Rainbow babywalkers!

(assume this is from like RTR block, with scavenge)
Baby Vraska
Legendary Planeswalker - Vraska
{+1} Put a +1/+1 counter on up to one target creature. It gets -2/-2 until the start of your next turn.
{-2} Target creature you control gains deathtouch until end of turn and must be blocked this turn if able.
{-8} You get an emblem with "Creatures you control with counters on them have indestructible."
{4}

Yeska, Blood Arcanist
Legendary Planeswalker - Yeska
{+1} Scry 1. You gain 1 life.
{-1} Draw a card. Each player loses 1 life.
{-7} You get an emblem with "whenever you gain or lose life, draw that many cards." Target player loses 4 life, and you gain 4 life.
{3}

Baby Tibalt
Legendary Planeswalker - Domri
{+1} Create a 1/1 red devil creature token with haste and "this creature attacks each combat if able, and can't block".
{-3} Target player draws two cards and loses 2 life.
{-8} Each player draws seven cards. At the end of their next turn, they lose life equal to the number of cards in their hand.
{3}

Baby Narset
Legendary Planeswalker - Narset
{+1} Creatures you control gain prowess until your next turn.
{-2} Look at the top five cards of your library. You may reveal a nonland, noncreature card from among them and put it into your hand. But the rest on the bottom of your library in a random order.
{-8} You get an emblem with "whenever you cast a noncreature spell, draw a card."
{4}

Baby Ral
Legendary Planeswalker - Ral
{+1} Draw a card, then discard a card.
{-2} Target instant or sorcery card in your graveyard gains flashback until your next turn. Its flashback cost is equal to its mana cost.
{-8} You get an emblem with "whenever you draw a card, this emblem deals 3 damage to any target".
{4}

And some UBwalkers I made because I love UB

Kid Tezz
Legendary Planeswalker - Tezzeret
{+1} Untap up to one target artifact. It becomes a 5/5 creature until your next turn.
{-1} Create a colorless powerstone artifact token with ": Add ".
{-6} Search your library for any number of artifact cards with different converted mana cost, reveal them, and put them into your hand. Then, shuffle your library.
{3}

Yeska, Sanguinologist
Legendary Planeswalker - Yeska
{+2} Draw a card. Target player loses 1 life, and you gain 1 life.
{-4} ~ deals damage to any target equal to the number of cards in your hand. You gain that much life.
{-10} You get an emblem with "Pay 1 life: draw a card".
{5}

Seliskis, Silent Slinker
Legendary Creature - Naga Assassin
Flash
When ~ enters the battlefield, target creature gets =1/-1 until end of turn for each assassin you control. If that creature would die this turn, put it on top of its owner's library instead.
3/3
The last thing the sentry felt was muscular coils around her throat. An hour later, she woke up without her helmet, tabard, or job.

Take Apart
Instant
Exile target permanent if mana of one of that permanent's colors was spent to cast ~.

Psychic Pain
Instant
~ deals 3 damage to any target. If that target was a player, they draw two cards.

Forbidden Secrets
Enchantment
Whenever you draw a card, put an omen counter on ~.
Sacrifice ~: ~ deals damage to each creature equal to the number of omen counters on it.

Alek, Hand of Despots
Legendary Planeswalker - Alek
{+1} Tap target creature. It gets -2/-0 until your next turn.
{-2} Create a 2/2 white and black knight creature token with deathtouch and vigilance.
{-6} Return each creature card in your graveyard with converted mana cost three or less to the battlefield. Each opponent loses life equal to twice the number of creatures you control, and you gain that much life.
{2}

Sebastian the Augmented
Legendary Creature - Human Wizard Warrior
Trample
Whenever you cast a noncreature spell put a +1/+1 counter on ~.
Whenever you cast a creature spell, it enters the battlefield with a +1/+1 counter on it.
3/3

Sebastian Evolved
Legendary Creature - Human Wizard Warrior
Whenever a player casts a spell, put a +1/+1 counter on ~.
At the beginning of each combat, choose one of flying, first strike, trample, haste, menace, vigilance, deathtouch, or hexproof. ~ gains that ability until end of turn.
3/3

Sebastian, Engineered Spark
Legendary Planeswalker - Sebastian
{+2} Draw a card. Put a +1/+1 counter on up to one target creature you control.
{-2} The next time you cast a spell this turn, ~ deals damage to any target equal to its converted mana cost.
{-10} You get an emblem with "At the beginning of your end step, search your library for a creature card and put it onto the battlefield, then shuffle your library."

Psychic pain is really flexible and is the kind of card I would jam in every RB deck I make ever

Salaris, Strength Stealer
Legendary Creature - Naga Wizard
When ~ enters the battlefield, put a +1/+1 counter on it for each creature you don't control.
Whenever a creature enters the battlefield under an opponent's control, put a +1/+1 counter on ~.
Creatures your opponents control get -1/-1.
3/3

Serfdom
Enchantment - Aura
Enchant creature
: Tap enchanted creature. If enchanted creature is tapped this way, add one mana of any color.

Alek Kingsworn
Legendary Planeswalker - Alek
{+1} Create a 2/2 White and Black knight creature with first strike
{-3} Put a +1/+1 counter on each creature you control. They gain lifelink, deathtouch, and vigilance until your next turn.
{-8} You get an emblem with "At the beginning of each end step, create a 2/2 White and Black knight creature token for each creature or planeswalker that died under your control this turn."
{5}

Resilient Baloth
Creature - Beast
Hexproof
~ can't be countered
Whenever an opponent casts a spell during your turn, put a +1/+1 counter on ~.
3/3

Some pre-spark walkers:

Yeska, Ambitious Researcher
Legendary Creature - Human Wizard
: Draw a card, then discard a card unless you pay 4 life.
2/2
"Knowledge is Power. Curiosity is Ambition."

Alek, Royal Enforcer
Legendary Creature - Human Knight
First Strike, Lifelink, Vigilance
As long as your life total is greater than the life total of the opponent with the lowest life total by 10 or more, creatures you control get +1/+1.
2/2
"Every one of us was created for a purpose. Yours is to kneel."

Otherworldly Contractor
Creature - Wraith Assassin
Kicker
Deathtouch
When ~ enters the battlefield, if it was kicked, destroy target creature with converted mana cost X.
2/2
Leave an offering, speak a name, and come morning, both will have vanished without a trace.

Kalixzt, Phyrexian Assimilator
Legendary Planeswalker: Kalixzt
When ~ enters the battlefield, you may exile target creature until ~ leaves the battlefield.
{+1} Until end of turn, you may have Kalixzt become a copy of a permanent creature card exiled with ~.
{-3} Put a card exiled with ~ into its owner's graveyard.
{-2} Exile ~, then return it to the battlefield under its owner's control at the beginning of your next end step.
{3}

Blood Tithe
Instant
Choose one:
-Each player sacrifices two creatures
-Creatures get -3/-3 until end of turn.

Mindbend
Sorcery
Name a nonland card. Target opponent reveals their hand and discards a card with the chosen name. If they can't, they discard a card at random.

Resleski, Cunning Hexer
Legendary Creature - Vampire Wizard Rogue
Whenever ~ attacks and isn't blocked, you may pay . If you do, search your library for a nonland card with converted mana cost X that could target that player, and cast it without paying its mana cost. If you do, shuffle your library.
Whenever ~ blocks or becomes blocked by a creature, you may pay . If you do, search your library for a nonland card with converted mana cost X that could target that creature, and cast it without paying its mana cost. If you do, shuffle your library.
3/3

Mana Well
Instant
Counter target spell unless its controller pays .
Storm

Pandemic
Instant
Target creature gets -1/-1 until end of turn.
Storm

A cycle of duals!

Grazing Pasture
Land
~ enters the battlefield tapped unless you have it enter the battlefield with a depletion counter on it.
: Add or . If ~ has a depletion counter on it, add instead.

Zealous Strike
Instant
Target creature gets +1/+0 and gains first strike until end of turn.
Storm

Nahiri, Stoneforge Savant
Legendary Planeswalker - Nahiri
{+1} Until end of turn, equip abilities of equipment you control cost less to activate.
{0} Creature a 1/1 white Kor Ally creature token with "This creature gets +1/+1 for each equipment attached to it."
{-2}Search your library for an equipment card, reveal it, and put it into your hand. Then, shuffle your library.
{4}

Decree of Prohibition
Enchantment
When ~ enters the battlefield, name a card.
Your opponents can't cast spells of the chose name.

Netherscope
Artifact
When ~ enters the battlefield, draw a card.
Reveal a card from your hand and pay its mana cost: exile that card. Activate this ability only any time you could cast a sorcery.
: You may cast a card exiled with ~ without paying its mana cost.

Conservative Cardinal
Creature - Human Cleric
Spells each player casts cost more to cast for each spell that player has cast this turn.
2/2
"I have seen far too much change in far too little time."

Netherwell Dweller
Creature - Elemental
Flying
Whenever ~ deals combat damage to a player, that player puts the top 2 cards of their library into their graveyard.
Sacrifice ~: counter each spell you don't control with the same name as a card in its owner's graveyard.
2/2