This is a cool idea. It's very Time Spiral-ey, and a cute way of paying homage to magic's past cards. I could see several mega cycles of cards like this, similar to spellshapers.
Here's some ideas on a slightly different way of executing the concept.
Stomping Giant3RR
Creature - Giant
Trample
Whenever Stomping Giant attacks, if there's a card named Tremor in your graveyard, Stomping Giant deals 4 damage to any target.
5/4
Disciple of Dosan1GG
Creature - Human Monk
Vigilance
Disciple of Dosan has hexproof as long as there's a card named Dosan's Oldest Chant in your graveyard.
3/3
Summoner's Maneuver1GU
Instant
Look at the top five cards of your library. You may reveal up to X creature cards from among them, where X is the number of players. Put the revealed cards into your hand and the rest on the bottom of your library in any order.
Timberland Outriders3(R/G)
Creature – Hound Warrior
Basic Landcycling 2G(2G, Discard this card: Search your library for a basic land card, reveal it, and put it into your hand. Then shuffle your library.)
Dash 1R(You may cast this spell for its dash cost. If you do, it gains haste, and it’s returned from the battlefield to its owner’s hand at the beginning of the next end step.)
3/2
Protector of RavnicaWUBRG
Creature - Avatar (R)
Hexproof from monocolored
Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
As long as you have the city's blessing, other creatures you control have "T: Add two mana of different colors."
7/7
Meet Thy Maker1BGU
Sorcery [M]
If your devotion to one or more colors is six or greater, you may put a God creature card of that color from your hand or graveyard onto the battlefield. Then each player sacrifices a creature.
Bestial Instinct2RG
Sorcery (U)
Choose one -
* Gain control of target creature until end of turn. Untap it. It gains haste until end of turn.
* Target creature gets +4/+4 until end of turn.
Entwine - Tap an untapped Beast you control. (Choose both if you pay the entwine cost.)
Refreshing the Herd3WB
Sorcery (R)
Target player sacrifices all creatures they control, then that player creates three 0/1 white Goat creature tokens and gains 3 life.
Sylvan Siegecraft1G
Instant (C)
Target Forest you control becomes a 3/3 green Elf Warrior creature with haste and reach until end of turn. It’s still a land.
Reinforce 1 - 3GG(3GG, Discard this card: Put a +1/+1 counter on target creature.)
A deck can have any number of cards named Sylvan Siegecraft.
Deceptive Wish2UB
Sorcery [M]
You may choose three cards you own from outside the game and separate them into two face up piles. An opponent chooses one of those piles. You put the chosen pile into your hand and return the other pile. Exile Deceptive Wish.
Heist Trap3UB
Instant - Trap
If an opponent had an artifact enter the battlefield under their control this turn, you may pay 0 rather than pay this spell's mana cost.
Create a 2/2 blue and black Rogue Artificer creature token with deathtouch, "X, T: Scry X," and "When this creature enters the battlefield, gain control of all artifacts for as long as you control this creature. Untap those artifacts."
Falling Feathers2(W/U)
Enchantment [U]
Whenever a creature you control with flying enters or leaves the battlefield, investigate. (Create a colorless Clue artifact token with "2, Sacrifice this artifact: Draw a card.")
I would be curious to see the untap symbol used a bit more as a little quest/game you try and find a way to complete.
Firebeacon Fort3
Artifact Creature - Wall (U)
Defender 1RW, q: Firebeacon Fort deals 4 damage to any target and you create a 1/1 white Soldier creature token with vigilance.
1/4
Perplexing Cube4
Artifact (R) 1, q: Add CCC. 2, q: Create a 1/1 colorless Servo artifact creature token. 3, q: Draw a card. 4, q: Exile target permanent unless its controller pays 4.
^OK, so that one above would probably be a bummer to open in limited, though it would likely be in a set with something like improvise.
Izzet Tornado-Wagon3
Artifact - Vehicle (U) U, q: Return up to three target creatures to their owner's hands. Draw a card.
Crew 5 (Tap any number of creatures you control with power 5 or more: This vehicle becomes an artifact creature until end of turn.)
3/3
Despoiled Armory
Artifact [U] T: Add C. 1(R/P)(R/P), T, Sacrifice Despoiled Armory: Attach all Equipment on the battlefield to target creature you control. That creature gains haste and infect until end of turn. Activate this ability only any time you could cast a sorcery. (Control of that Equipment doesn’t change.)
Urn of Regrets3
Artifact
Whenever a source an opponent controls deals damage to you, if Urn of Regrets is untapped, put a -1/-1 counter on up to one target creature. 1, Remove a -1/-1 counter from a creature you control: Draw a card.
I've always been interested in effects like this that could perhaps be a bit more attractive in limited.
Throughtwrench Imp1BB
Creature - Imp (C) B, Discard this card: Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.
Activate this ability only any time you could cast a sorcery.
2/1
Menacing TiradeB
Sorcery (C)
Choose one -
Target creature gains menace until end of turn.
Target opponent reveals their hand. You choose an artifact or enchantment card from it. That player discards that card.
Thought Needle0
Artifact (C) 2, T, Sacrifice Thought Needle: Scry 1. B, T, Sacrifice Thought Needle: Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card. Activate this ability only any time you could cast a sorcery.
Stoneskin Sneak1
Creature - Gargoyle (U)
Flying, defender
When Stoneskin Sneak enters the battlefield, you may pay B. If you do, target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.
1/1
Devour Secrets1U
Sorcery (U)
Kicker 1B(You may pay an additional 1B as you cast this.)
Each player draws two cards. If this spell was kicked, target opponent reveals their hand. You choose up to two instant and/or sorcery cards from it. That player discards those cards.
Here's some ideas on a slightly different way of executing the concept.
Stomping Giant 3RR
Creature - Giant
Trample
Whenever Stomping Giant attacks, if there's a card named Tremor in your graveyard, Stomping Giant deals 4 damage to any target.
5/4
Disciple of Dosan 1GG
Creature - Human Monk
Vigilance
Disciple of Dosan has hexproof as long as there's a card named Dosan's Oldest Chant in your graveyard.
3/3
Summoner's Maneuver 1GU
Instant
Look at the top five cards of your library. You may reveal up to X creature cards from among them, where X is the number of players. Put the revealed cards into your hand and the rest on the bottom of your library in any order.
Timberland Outriders 3(R/G)
Creature – Hound Warrior
Basic Landcycling 2G (2G, Discard this card: Search your library for a basic land card, reveal it, and put it into your hand. Then shuffle your library.)
Dash 1R (You may cast this spell for its dash cost. If you do, it gains haste, and it’s returned from the battlefield to its owner’s hand at the beginning of the next end step.)
3/2
Protector of Ravnica WUBRG
Creature - Avatar (R)
Hexproof from monocolored
Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
As long as you have the city's blessing, other creatures you control have "T: Add two mana of different colors."
7/7
Meet Thy Maker 1BGU
Sorcery [M]
If your devotion to one or more colors is six or greater, you may put a God creature card of that color from your hand or graveyard onto the battlefield. Then each player sacrifices a creature.
Bestial Instinct 2RG
Sorcery (U)
Choose one -
* Gain control of target creature until end of turn. Untap it. It gains haste until end of turn.
* Target creature gets +4/+4 until end of turn.
Entwine - Tap an untapped Beast you control. (Choose both if you pay the entwine cost.)
Refreshing the Herd 3WB
Sorcery (R)
Target player sacrifices all creatures they control, then that player creates three 0/1 white Goat creature tokens and gains 3 life.
Sylvan Siegecraft 1G
Instant (C)
Target Forest you control becomes a 3/3 green Elf Warrior creature with haste and reach until end of turn. It’s still a land.
Reinforce 1 - 3GG (3GG, Discard this card: Put a +1/+1 counter on target creature.)
A deck can have any number of cards named Sylvan Siegecraft.
Deceptive Wish 2UB
Sorcery [M]
You may choose three cards you own from outside the game and separate them into two face up piles. An opponent chooses one of those piles. You put the chosen pile into your hand and return the other pile. Exile Deceptive Wish.
Heist Trap 3UB
Instant - Trap
If an opponent had an artifact enter the battlefield under their control this turn, you may pay 0 rather than pay this spell's mana cost.
Create a 2/2 blue and black Rogue Artificer creature token with deathtouch, "X, T: Scry X," and "When this creature enters the battlefield, gain control of all artifacts for as long as you control this creature. Untap those artifacts."
Falling Feathers 2(W/U)
Enchantment [U]
Whenever a creature you control with flying enters or leaves the battlefield, investigate. (Create a colorless Clue artifact token with "2, Sacrifice this artifact: Draw a card.")
Firebeacon Fort 3
Artifact Creature - Wall (U)
Defender
1RW, q: Firebeacon Fort deals 4 damage to any target and you create a 1/1 white Soldier creature token with vigilance.
1/4
Perplexing Cube 4
Artifact (R)
1, q: Add CCC.
2, q: Create a 1/1 colorless Servo artifact creature token.
3, q: Draw a card.
4, q: Exile target permanent unless its controller pays 4.
^OK, so that one above would probably be a bummer to open in limited, though it would likely be in a set with something like improvise.
Izzet Tornado-Wagon 3
Artifact - Vehicle (U)
U, q: Return up to three target creatures to their owner's hands. Draw a card.
Crew 5 (Tap any number of creatures you control with power 5 or more: This vehicle becomes an artifact creature until end of turn.)
3/3
(I dunno why I posted only artifacts lol.)
Despoiled Armory
Artifact [U]
T: Add C.
1(R/P)(R/P), T, Sacrifice Despoiled Armory: Attach all Equipment on the battlefield to target creature you control. That creature gains haste and infect until end of turn. Activate this ability only any time you could cast a sorcery. (Control of that Equipment doesn’t change.)
Urn of Regrets 3
Artifact
Whenever a source an opponent controls deals damage to you, if Urn of Regrets is untapped, put a -1/-1 counter on up to one target creature.
1, Remove a -1/-1 counter from a creature you control: Draw a card.
Throughtwrench Imp 1BB
Creature - Imp (C)
B, Discard this card: Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.
Activate this ability only any time you could cast a sorcery.
2/1
Menacing Tirade B
Sorcery (C)
Choose one -
- Target creature gains menace until end of turn.
- Target opponent reveals their hand. You choose an artifact or enchantment card from it. That player discards that card.
Thought Needle 0Artifact (C)
2, T, Sacrifice Thought Needle: Scry 1.
B, T, Sacrifice Thought Needle: Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card. Activate this ability only any time you could cast a sorcery.
Stoneskin Sneak 1
Creature - Gargoyle (U)
Flying, defender
When Stoneskin Sneak enters the battlefield, you may pay B. If you do, target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.
1/1
Devour Secrets 1U
Sorcery (U)
Kicker 1B (You may pay an additional 1B as you cast this.)
Each player draws two cards. If this spell was kicked, target opponent reveals their hand. You choose up to two instant and/or sorcery cards from it. That player discards those cards.