Ordeal of Thassa

Enchant creature
Whenever enchanted creature attacks, put a +1/+1 counter on it. Then if it has three or more +1/+1 counters on it, sacrifice Ordeal of Thassa.
When you sacrifice Ordeal of Thassa, draw two cards.

Armory of Iroas

Whenever equipped creature attacks, put a +1/+1 counter on it.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Walking Ballista

Walking Ballista enters the battlefield with X +1/+1 counters on it.
{4}: Put a +1/+1 counter on Walking Ballista.
Remove a +1/+1 counter from Walking Ballista: It deals 1 damage to any target.

Gideon Jura

+2: During target opponent's next turn, creatures that player controls attack Gideon Jura if able.
−2: Destroy target tapped creature.
0: Until end of turn, Gideon Jura becomes a 6/6 Human Soldier creature that's still a planeswalker. Prevent all damage that would be dealt to him this turn.

Ring of Evos Isle

{2}: Equipped creature gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)
At the beginning of your upkeep, put a +1/+1 counter on equipped creature if it's blue.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Throw a Line

Distribute two +1/+1 counters among one or two target creatures. (Then exile this card. You may cast the creature later from exile.)

Ondu Knotmaster

Lifelink
Whenever another modified creature you control dies, put two +1/+1 counters on Ondu Knotmaster.

Ondu Knotmaster // Throw a Line

Ordeal of Heliod

Enchant creature
Whenever enchanted creature attacks, put a +1/+1 counter on it. Then if it has three or more +1/+1 counters on it, sacrifice Ordeal of Heliod.
When you sacrifice Ordeal of Heliod, you gain 10 life.

Bind Spirit

Return target creature card from your graveyard to your hand. (Then exile this card. You may cast the artifact later from exile.)

Ghost Lantern

Whenever a creature you control dies, put a +1/+1 counter on equipped creature.
Equip {1}

Ghost Lantern // Bind Spirit

Necrosynthesis

Enchant creature
Enchanted creature has "Whenever another creature dies, put a +1/+1 counter on this creature."
When enchanted creature dies, look at the top X cards of your library, where X is its power. Put one of those cards into your hand and the rest on the bottom of your library in a random order.

Ring of Xathrid

{2}: Regenerate equipped creature. (The next time that creature would be destroyed this turn, it isn't. Instead tap it, remove all damage from it, and remove it from combat.)
At the beginning of your upkeep, put a +1/+1 counter on equipped creature if it's black.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Pearl-Ear, Imperial Advisor

Lifelink
Enchantment spells you cast have affinity for Auras. (They cost {1} less to cast for each Aura you control.)
Whenever you cast an Aura spell that targets a modified permanent you control, draw a card. (Equipment, Auras you control, and counters are modifications.)

T-45 Power Armor

When T-45 Power Armor enters the battlefield, you get {E}{E} (two energy counters).
Equipped creature gets +3/+3 and doesn't untap during its controller's untap step.
At the beginning of your upkeep, you may pay {E}. If you do, untap equipped creature, then put your choice of a menace, trample, or lifelink counter on it.
Equip {3}

Gideon, Champion of Justice

+1: Put a loyalty counter on Gideon, Champion of Justice for each creature target opponent controls.
0: Until end of turn, Gideon, Champion of Justice becomes a Human Soldier creature with power and toughness each equal to the number of loyalty counters on him and gains indestructible. He's still a planeswalker. Prevent all damage that would be dealt to him this turn.
−15: Exile all other permanents.

Pip-Boy 3000

Whenever equipped creature attacks, choose one —
• Sort Inventory — Draw a card, then discard a card.
• Pick a Perk — Put a +1/+1 counter on that creature.
• Check Map — Untap up to two target lands.
Equip {2}

Sram, Senior Edificer

Whenever you cast an Aura, Equipment, or Vehicle spell, draw a card.

Eternal Thirst

Enchant creature
Enchanted creature has lifelink and "Whenever a creature an opponent controls dies, put a +1/+1 counter on this creature." (Damage dealt by a creature with lifelink also causes its controller to gain that much life.)

Ephara's Enlightenment

Enchant creature
When Ephara's Enlightenment enters the battlefield, put a +1/+1 counter on enchanted creature.
Enchanted creature has flying.
Whenever a creature enters the battlefield under your control, you may return Ephara's Enlightenment to its owner's hand.

Gideon of the Trials

+1: Until your next turn, prevent all damage target permanent would deal.
0: Until end of turn, Gideon of the Trials becomes a 4/4 Human Soldier creature with indestructible that's still a planeswalker. Prevent all damage that would be dealt to him this turn.
0: You get an emblem with "As long as you control a Gideon planeswalker, you can't lose the game and your opponents can't win the game."

Gideon, the Oathsworn

Whenever you attack with two or more non-Gideon creatures, put a +1/+1 counter on each of those creatures.
+2: Until end of turn, Gideon, the Oathsworn becomes a 5/5 white Soldier creature that's still a planeswalker. Prevent all damage that would be dealt to him this turn. (He can't attack if he was cast this turn.)
−9: Exile Gideon, the Oathsworn and each creature your opponents control.

Sword of Hours

Whenever equipped creature attacks, put a +1/+1 counter on it.
Whenever equipped creature deals combat damage, roll a d12. If the result is greater than the damage dealt or the result is 12, double the number of +1/+1 counters on that creature.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Ring of Thune

Equipped creature has vigilance. (Attacking doesn't cause it to tap.)
At the beginning of your upkeep, put a +1/+1 counter on equipped creature if it's white.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Tarrian's Soulcleaver

Equipped creature has vigilance.
Whenever another artifact or creature is put into a graveyard from the battlefield, put a +1/+1 counter on equipped creature.
Equip {2}

Snake Cult Initiation

Enchant creature
Enchanted creature has poisonous 3. (Whenever it deals combat damage to a player, that player gets three poison counters. A player with ten or more poison counters loses the game.)

Necrogen Communion

Enchant creature you control
Enchanted creature has toxic 2. (Players dealt combat damage by it also get two poison counters.)
When enchanted creature dies, return that card to the battlefield under your control.

Luxior, Giada's Gift

Equipped creature gets +1/+1 for each counter on it.
Equipped permanent isn't a planeswalker and is a creature in addition to its other types. (Loyalty abilities can still be activated.)
Equip planeswalker {1}
Equip {3}

Arna Kennerüd, Skycaptain

Flying, lifelink
Ward—Discard a card.
Whenever a modified creature you control attacks, double the number of each kind of counter on it. Then for each nontoken permanent attached to it, create a token that's a copy of that permanent attached to that creature.

Envoy of the Ancestors

Outlast {W} ({W}, {T}: Put a +1/+1 counter on this creature. Outlast only as a sorcery.)
Modified creatures you control have lifelink. (Equipment, Auras you control, and counters are modifications.)

Gideon Blackblade

As long as it's your turn, Gideon Blackblade is a 4/4 Human Soldier creature with indestructible that's still a planeswalker.
Prevent all damage that would be dealt to Gideon Blackblade during your turn.
+1: Up to one other target creature you control gains your choice of vigilance, lifelink, or indestructible until end of turn.
−6: Exile target nonland permanent.

Blade of the Bloodchief

Whenever a creature dies, put a +1/+1 counter on equipped creature. If equipped creature is a Vampire, put two +1/+1 counters on it instead.
Equip {1}

Holy Frazzle-Cannon

Whenever equipped creature attacks, put a +1/+1 counter on that creature and each other creature you control that shares a creature type with it.
Equip {1}

Invasion of New Capenna

(As a Siege enters, choose an opponent to protect it. You and others can attack it. When it's defeated, exile it, then cast it transformed.)
When Invasion of New Capenna enters the battlefield, you may sacrifice an artifact or creature. When you do, exile target artifact or creature an opponent controls.

Invasion of New Capenna // Holy Frazzle-Cannon

Andúril, Narsil Reforged

Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
Whenever equipped creature attacks, put a +1/+1 counter on each creature you control. If you have the city's blessing, put two +1/+1 counters on each creature you control instead.
Equip {3}

Greatsword of Tyr

Whenever equipped creature attacks, put a +1/+1 counter on it and tap up to one target creature defending player controls.
Equip {W} ({W}: Attach to target creature you control. Equip only as a sorcery.)

Thran Power Suit

Equipped creature gets +1/+1 for each Aura and Equipment attached to it and has ward {2}. (Whenever equipped creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Unforgiving One

Menace (This creature can't be blocked except by two or more creatures.)
Whenever Unforgiving One attacks, return target creature card with mana value X or less from your graveyard to the battlefield, where X is the number of modified creatures you control. (Equipment, Auras you control, and counters are modifications.)

Ordeal of Erebos

Enchant creature
Whenever enchanted creature attacks, put a +1/+1 counter on it. Then if it has three or more +1/+1 counters on it, sacrifice Ordeal of Erebos.
When you sacrifice Ordeal of Erebos, target player discards two cards.

Mask of the Schemer

Whenever equipped creature deals combat damage to a player, it connives X, where X is the amount of damage it dealt to that player. (Draw X cards, then discard X cards. Put a +1/+1 counter on that creature for each nonland card discarded this way.)
Equip {2}

Gideon, Ally of Zendikar

+1: Until end of turn, Gideon, Ally of Zendikar becomes a 5/5 Human Soldier Ally creature with indestructible that's still a planeswalker. Prevent all damage that would be dealt to him this turn.
0: Create a 2/2 white Knight Ally creature token.
−4: You get an emblem with "Creatures you control get +1/+1."

Gleam of Authority

Enchant creature
Enchanted creature gets +1/+1 for each +1/+1 counter on other creatures you control.
Enchanted creature has vigilance and "{W}, {T}: Bolster 1." (To bolster 1, choose a creature with the least toughness among creatures you control and put a +1/+1 counter on it.)