Wilbur, the Prince's Brother
Legendary Creature — Boar Mutant
At the beginning of combat during your turn, put a marked counter on target creature. (Spells that target marked creatures cost less to cast.)
Whenever a creature deals combat damage to Wilbur, put a marked counter on that creature.
When Wilbur dies, target Boar you control deals damage equal to its power to each marked creature an opponent controls.
1/1

Impeccable Dancer
Creature — Efreet Performer
Flying
Impeccable Dancer enters the battlefield with a +1/+1 counter.
Whenever you cast an instant or sorcery spell, copy that spell and put a +1/+1 counter on Impeccable Dancer if that spell's mana value is equal to the number of +1/+1 counters on Impeccable Dancer. You may choose new targets for the copy. Otherwise, remove all +1/+1 counters from Impeccable Dancer.
0/0

@neru: it needs to have portal or dancer in the name.

Yep, missed the new page.

Second Prince's Portal
Legendary Enchantment
At the beginning of your upkeep, you may become the monarch.
At the beginning of each player's end step, if that player isn't the monarch, they create a tapped Treasure token.
"Why should I concern myself with succeeding both my father and my eldest brother? Let them handle the trouble of politics, or at least let me indulge myself with the finer benefits of being a royal."

... blah ... ok actual submission due to the edit prior

Impeccable Timing
Enchantment
Cards you own have Miracle. Their Miracle cost is equal to their mana cost.
Whenever you cast a spell for its Miracle cost, you may add one mana of any type spent to cast that spell at the beginning of your precombat main phase.
"Just what we needed, when we needed it."

Throw Off Timing
Instant
Choose one—

• Target creature loses first strike and double strike. Each creature blocking or blocked by it gains first strike.
• Until end of turn, permanents you don't control enter the battlefield tapped.
• Exile target spell. At the beginning of the next upkeep, that spell's controller may cast that spell without paying its mana cost.

In many ways, Teferi is still that disruptive student.

Empty Throw
Instant
Return target noncreature spell to its owner's hand. If you control that spell, the next noncreature spell you cast this turn can't be countered.
Ojutai martial masters understand the threat of an attack can leave an opponent more vulberable than the attack itself.

https://www.dustloop.com/w/Kara_Cancel# ... us%20empty).

Had fighting games on my mind with this.

Empty Threats -
Instant
Target creature you do not control gains indestructible until end of turn. Then, ~ deals 7 damage to that creature.
Mazzlo flexed his muscles, made threatening gestures and promised pain and suffering upon his would-be victim. All of which was met with a stoic stare.

Threaten with a Good Time
Instant
Exile target creature. Its controller may roll to visit their Attractions.
"It's a good thing you'll never want to leave." — "Brims" Barone, midway mobster

Don't You Dare Threaten Me -
Instant
If a black or red spell is targeting you, you may cast this card without paying its mana cost.
Counter target spell targeting you.
"You have been warned."

You Play Truth or Dare
Sorcery
Choose one:

• Truth - Each player reveals their hand.
• Dare - Name a nonland card. Until your next turn, the named card can't be played.

Rebound

Truth of the Heart
Instant
As an additional cost to cast this spell, discard a card.
Choose a card name. Reveal the top seven cards on your library. You may put up to one card with the chosen name and up to one random card from among those cards in your hand. Put the rest on the bottom of your library in random order.

FYI, my bad mechanic that uses -1/-1 counters and +1/+1 counters in the same set: Alignment (As this creature enters the battlefield, choose good or evil. If you chose good, it enters the battlefield with a +1/+1 counter on it. If you chose evil, it enters with a -1/-1 counter on it.)

Heart of the Cards
Instant
Shuffle, then reveal the top card on your library or reveal the top three cards on your library if this spell was cast with its miracle cost. Put each land card revealed this way on the battlefield, untap it, and it gains "At the beginning of your end step, sacrifice this land." Cast each nonland card revealed this way without paying its mana cost. Choose the targets of each instant or sorcery spell cast this way at random. Each permanent spell cast this way has haste and "At the beginning of your end step, sacrifice this permanent."
Miracle

Read the Cards -
Sorcery
Draw cards equal to the number of cards in your hand and separate the cards in your hand into two piles face-down. You may turn any of the cards face-up instead as you separate them into their piles. Then, an opponent chooses one of the pile. For the chosen pile, put all the cards into your graveyard face-up and return the other pile to your hand.
You have no maximum hand size until your next turn.

Room of Requirement
Legendary Land
: Add .
Whenever Room of Requirement becomes tapped, mill a card. Then, you may sacrifice Room of Requirement. If you do, put that card on top of your library.

Room Service
Artifact - Food
, , Sacrifice ~: You gain 3 life.
, , Return ~ to its owner's hand: Each player gains 3 life.
"Nothin' keeps things civil like good hospitapitality!"

Civil Service
Enchantment
As an additional cost to cast your first spell each turn, you may tap any number of untapped Advisors you control. The spell costs less to cast for each Advisor tapped this way.
At the beginning of your end step, each player draws X cards then discards X cards, where X is the number of tapped Advisors you control.
"Whether you pick up a blade or a pen, you serve the state. That is all that matters." — Seneschal Liao

Mercenary Service -
Sorcery
Search your library for a mercenary creature card with mana cost X or less and put it onto the battlefield. Then, shuffle your library. If three or more mana from Treasures were spent to cast ~, mercenaries you control gets +1/+0 and has haste until end of turn.
They held loyalties to no state, country nor kingdom. Only the promise of coin brings their blades to the table.