Witness Protection

Enchant creature
Enchanted creature loses all abilities and is a green and white Citizen creature with base power and toughness 1/1 named Legitimate Businessperson. (It loses all other colors, card types, creature types, and names.)

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Surge Engine

Defender
{U}: Surge Engine loses defender and gains "This creature can't be blocked."
{2}{U}: Surge Engine becomes blue and has base power and toughness 5/4. Activate only if Surge Engine doesn't have defender.
{4}{U}{U}: Draw three cards. Activate only if Surge Engine is blue and only once.

Realm-Scorcher Hellkite

Bargain (You may sacrifice an artifact, enchantment, or token as you cast this spell.)
Flying, haste
When Realm-Scorcher Hellkite enters, if it was bargained, add four mana in any combination of colors.
{1}{R}: Realm-Scorcher Hellkite deals 1 damage to any target.

Consider

Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
Draw a card.

Omen Hawker

{T}: Add {C}{U}. Spend this mana only to activate abilities.

Otawara, Soaring City

{T}: Add {U}.
Channel — {3}{U}, Discard Otawara, Soaring City: Return target artifact, creature, enchantment, or planeswalker to its owner's hand. This ability costs {1} less to activate for each legendary creature you control.

Sleight of Hand

Look at the top two cards of your library. Put one of them into your hand and the other on the bottom of your library.

Rona, Tolarian Obliterator

Trample
Whenever a source deals damage to Rona, Tolarian Obliterator, that source's controller exiles a card from their hand at random. If it's a land card, you may put it onto the battlefield under your control. Otherwise, you may cast it without paying its mana cost.

Rona, Herald of Invasion

Whenever you cast a legendary spell, untap Rona, Herald of Invasion.
{T}: Draw a card, then discard a card.
{5}{B/P}: Transform Rona. Activate only as a sorcery. ({B/P} can be paid with either {B} or 2 life.)

Rona, Herald of Invasion // Rona, Tolarian Obliterator

Hypnotic Grifter

{3}: Hypnotic Grifter connives. (Draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on this creature.)

Training Grounds

Activated abilities of creatures you control cost {2} less to activate. This effect can't reduce the mana in that cost to less than one mana.

Agatha's Soul Cauldron

You may spend mana as though it were mana of any color to activate abilities of creatures you control.
Creatures you control with +1/+1 counters on them have all activated abilities of all creature cards exiled with Agatha's Soul Cauldron.
{T}: Exile target card from a graveyard. When a creature card is exiled this way, put a +1/+1 counter on target creature you control.

Island

Make Disappear

Casualty 1 (As you cast this spell, you may sacrifice a creature with power 1 or greater. When you do, copy this spell and you may choose a new target for the copy.)
Counter target spell unless its controller pays {2}.

Sleep-Cursed Faerie

Flying, ward {2}
Sleep-Cursed Faerie enters tapped with three stun counters on it. (If it would become untapped, remove a stun counter from it instead.)
{1}{U}: Untap Sleep-Cursed Faerie.