Aren't Humans and Spirits always both in harmony or both not in harmony? I think it would just make more sense if it just counted the difference and made tokens based on it.

Ride the Falling Waters
Instant — Arcane
Return any number of cards with splice from your graveyard to your hand. Play with them revealed until end of turn. You can't cast those cards. At the beginning of the next end step, exile those cards. Exile this spell.
Splice onto instant or sorcery

Iron-Spine Tessen
Artifact — Equipment
Equipped creature gets +1/+1.
: Equipped creature gets +1/+0 until end of turn.
: Equipped creature gets +0/+1 until end of turn.
Whenever a creature is put onto the battlefield under your control by a ninjutsu ability, if Iron-Spine Tessen was attached to a creature returned to a hand by that ability, attach Iron-Spine Tessen to that creature.
Equip

Bridge Between Worlds
Land (R)
: Add one mana of any color. You lose 2 life unless you control a permanent of that color.
The world of the kami and the world of mortals are separate no more.

Ravnica

Oath of the Soulsworn
Enchantment — Aura
Enchant creature
Enchanted creature has defender.
: You gain control of enchanted creature. It gains flying and lifelink.
"They say it's duty to a greater cause, but I can't see the difference between that and the ghost debtors of Orzhov." — Agrus Kos

Turn the Screws
Sorcery
Target opponent loses X life. If red mana was spent to cast this spell, that player sacrifices a creature at random.
Even Rakdo musicians must tune their instruments before every show. They twist screws and adjust vocal cords to assure their screamers hit the right notes.

Slumrunner
Creature — Viashino Shaman
Riot
Whenever a creature with haste you control attacks, add . Until end of turn, you don’t lose this mana as steps and phases end.
"This thunder is the beating of the Raze-Boar's hoofs! It is already too late for you!"
2/2

The Fathom Edict
Enchantment — Saga
I - Sacrifice a land. When you do, search your library for up to two Forest, Island, and/or Gate cards, put them onto the battlefield tapped, then shuffle.
II - Look at the top five cards on your library. Put a creature card from among them in your hand then put the rest in your graveyard.
III - Return target card from your graveyard to your hand, then shuffle your graveyard into your library.

Banner of the Guildpact

Artifact (R)
When Banner of the Guildpact enters the battlefield, choose two colors.
Each creature you control get +1/+1 for each of the chosen colors it is.

Inner Guildgate
Land — Gate
When Inner Guildgate enters the battlefield, choose a color pair.
: Add one mana of any color. Spend this mana only to cast spells that are exactly the colors of the chosen color pair or to activate abilities from a card or permanent that are exactly the colors of the chosen color pair.
Not to welcome but to keep out.

Next is Dominaria.

Visionary Sage
Creature — Human Wizard Spellshaper
, , Discard a card: Scry 1, then draw a card.
, , Sacrifice Visionary Sage, Discard a historic card: Draw three cards.
"I can see the threads of time but there are threads I am afraid to pull at."
1/1

Preceptor of the Perfected
Creature — Phyrexian Spellshaper
, , Discard a card: Return up to two target creature cards from your graveyard to your hand.
, , Discard a historic card, Sacrifice Preceptor of the Perfected: Until end of turn, you may play lands and cast spells from your graveyard. If a card would be put into your graveyard from anywhere this turn, exile that card instead.
4/1

Krosan Huntmaster
Creature — Elf Warrior
Provoke
Whenever Krosan Huntmaster provokes a creature, create a 3/3 green Beast creature token.
"Our home is not what it once was, but neither are me and my friends."
1/2

The Legions of Otaria
Enchantment — Saga
When The Legions of Otaria enters the battlefield, choose a creature type. Spells of the chosen type you cast cost less to cast as long as The Legions of Otaria remains on the battlefield.
I - Exile target creature an opponent controls.
II - Target opponent chooses a creature type then creates three 2/2 creature tokens of the chosen creature type.
III - You may return a creature card of the creature type you chose from your graveyard to the battlefield.

Tarnished Mox
Artifact
Kicker
When Tarnished Mox enters the battlefield, if it was kicked, put a charge counter on it.
: Add one mana of any color. Activate this ability only if Tarnished Mox has a charge counter.

Havenwood Cradle
Legendary Land (R)
: Add .
: Add for each Fungus and/or Saproling creature you control.
Thelon's children yet thrive in the ruins of those who sired them.

Next: Lorwyn/Shadowmoor