Underworld Lotus

Artifact
, Sacrifice Underworld Lotus: Add three mana of any one color. This mana can only be spent to cast soells from your graveyard or activate abilities of cards in your graveyard

Voltaic Lotus

Artifact
, Sacrifice Voltaic Lotus: You get (three energy counters).
"Day 13: New specimen found today. Seems to have absorbed aether through its roots. Appearance: Deep blue petals. Power: Unknown."
—Journal of Yara Atten, explorer and biologist

Xommox the Jeweler

Legendary Creature - Golem Artificer
: Add one mana of any color. An opponent gains control of Xommox.
0/1

Yeti Remains

Artifact
, Sacrifice Yeti Remains: Create three Food tokens. (They’re artifacts with “, , Sacrifice this artifact: You gain 3 life.”)
, Sacrifice Yeti Remains: Create a 5/5 black Zombie Yeti creature token.
Both the hill and swamp tribes hunt yetis, however they each have a different purpose in mind for their prey.

Keeping the combination of colorless and lands into one round, we're back at white.

Angel of Judgement
Creature — Angel
Flying, vigilance
When Angel of Judgement becomes tapped, destroy all creatures.
It is when she can no longer watch that it is time.
4/4

Battletide Tactics

Instant [U]
Choose one —
• Tap target creature. Creatures you control get +2/+0 until end of turn.
• Untap target creature. Creatures you control get +0/+2 until end of turn.
A skilled general can read the tides of battle like a ship captain reads the sea.

Crash
Instant (U)
Exile target creature crewing a vehicle.

Deter
Sorcery
Convoke
Until your next turn, spells cost (2) more to cast, activated abilities cost (2) more to activate, and each creature can't attack or block unless it's controller pays (2).

Ethical Oversight

Enchantment
Ideological Purity - As long as you control no permanents that are a color other than white, untap each creature you control at the beginning each main phase.

Family Style
Enchantment
Improvise
When this enchantment enters, create three Food tokens.
Foods you control have ", , Sacrifice this Food: Any number of target players each gains 2 life and draws a card. This ability costs less to activate for each opponent it targets."

Guild Recruiter

Creature -- Human Advisor [U]
When this creature enters, look at the top four cards of your library. You may reveal a creature card that's exactly two colors from among them and put it into your hand. Put the rest on the bottom of your library in a random order.
"You, sir, with the strong arms! Have you ever thought of becoming a legionnaire?"
2/3

Holy Inquisition

Enchantment - Aura
Enchant Player
Whenever enchanted player casts a nonwhite spell, they lose 1 life.
At the beginning of your upkeep, enchanted player may reveal their hand. If they do and they reveal no nonwhite, nonland cards this way, sacrifice Holy Inquisition and lose life equal to the number of cards revealed.

Incapacitate

Sorcery
Destroy target tapped creature an opponent controls.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)
"The generals tell me where to shoot, and I shoot. I don't care much for the targets."
—Djurhuus, 5th Batallion Sniper

My idea is to colour shift Cipher into white, flavoured as covert military communications.

Jailed
Sorcery (U)
If there are no creatures in exile, exile target creature. Otherwise, detain it.
You have to make an example.

Kellan's Example
Instant
Kellan's Example deals 2 damage to target attacking creature. If this spell was cast as an Adventure, this spell deals damage equal to the Adventuring creature card's power instead.
Leadership - As long as this card is in your graveyard and you control a legendary creature, each creature card you own has this Kellan's Example as an Adventure. (You may cast a creature card as this spell. As that spell resolves, exile that card and it may be cast from exile.)

Liberate Prisoners

Sorcery
Create two 1/1 white Soldier creature tokens.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)
The prisoner unfurled the secret message, it simply read one word: 'Tonight'.

North Star
Enchantment
Constellation - Whenever this enchantment or another enchantment you control enters, target creature you control explores.
Tap X untapped creatures you control, Sacrifice this enchantment: Return target creature card with mana value X from your graveyard to the battlefield.