So a thouhgtseize discard effect for additional U if nothing good just a peek.
Omnipotent Vanish WB
Instant (U)
Choose one
Put target instant or sorcery spell with converted mana cost 2 or less on top of its owner's library.
Put target permanent with converted mana cost 4 or more on top of its owner's library.
This could turn into fastbond with haste cards. The only note worthing this plants spread quickly. Maybe increasing its mana cost by 1 would make this balance.
Idea Snatch UB
Instant
Each opponent reveals his or her hand.
You may search your library for a card with the same name as a card revealed this way, put that card into your hand, then shuffle your library.
Draw a card at the beginning of the next end step if you didnt search your library this turn.
Your idea is more of an unstable like concept. Its difficult to make it happen need to rearrange every card I reconstruct your idea into an enchantment instead.
~ U
Enchantment
X: Exile up to X cards from the top of your library face down. Put that many cards from the bottom of your library on top in any order. Put the exiled cards at the bottom of your library in any order. Any player may activate this ability. X can't be 0.
Share Knowledge 1U
Enchantment
Instant and sorcery spells you cast cost 2 less to cast.
Whenever you cast an instant or sorcery spell, any of your opponents may copy that spell. Each of those players may choose new targets for his or her copy other than spells you control.
Thank you for creating an olivia walker that can be commander playable too! and it met the current progress of the story. Now for its ability, its all good as its 2nd ability lets you swing a vampire token for 4. Ultimate makes this more vampire friendly.
Ob Nixillis' VengeanceB
Instant (R)
Exile target nonblack planeswalker. Its controller loses 3 life.
Secrets of the Bandit1UU
Sorcery (R)
Each opponent exiles the top card of his or her library. You may cast a nonland card exiled this way without paying its mana cost.
Whenever your commander deals combat damage to a player, you may return Secrets of the Bandit from your graveyard to your hand.
Feels lot of things to be fixed here as you can't turn the creature into a noncreature with no other card type and Reaper's Blade gets unattached the moment the devotion isn't satisfied.
Blitz FrostU
Instant (R)
Blitz Frost deals 1 damage to target creature or player. If a creature is dealt damage this way, tap that creature unless its controller pays 2. If a player is dealt damage this way, that player can't cast creature spells this turn unless he or she pays 2.
Trying to Catch Up5G
Sorcery (U)
If an opponent controls three or more permanents that can be tapped for mana than you, you may pay G rather than pay Trying to Catch Up's mana cost.
Search your library for up to three basic Forest cards and put them onto the battlefield tapped, then shuffle your library.
Good design and a way to abuse the 2 so paying UUUU gives you a better version of Concentrate. As for rarity issue it should be a rare.
Astarot, Hell Plunger3BB
Legendary Creature - Demon (M)
Flash
Flying
Whenever Astarot, Hell Plunger enters or leaves the battlefield, exile target card from an opponent's graveyard. If you do, you may search your library for a card with the same name as that card, reveal it, put it into your hand, then shuffle your library.
4/4
Unwanted VisitorB
Creature - Zombie (R)
Unwanted Visitor enters the battlefield tapped.
Unwanted Visitor doesn't untap during your untap step.
Whenever a nonbasic land enters the battlefield under an opponent's control, untap Unwanted Visitor.
3/3
Cunning VampireRR
Creature - Vampire Wizard (R)
As an additional cost to cast Cunning Vampire, sacrifice a creature.
Flying
When Cunning Vampire enters the battlefield, if the sacrificed creature deals combat damage to a player this turn, that player sacrifices a permanent.
3/2
Thirteenth Hour1B
Sorcery (R)
Each player sacrifices a permanent and loses 1 life. If your life total or number of permanents you control is exactly 13, take an extra turn after this one.
Fake Gallery3UU
Instant (R)
If its your turn, Fake Gallery cost 5 more to cast.
Put a token onto the battlefield that's a copy of each nontoken, nonland permanent each of your opponent controls. Exile them at the beginning of the next end step.
Omnipotent Vanish WB
Instant (U)
Choose one
Put target instant or sorcery spell with converted mana cost 2 or less on top of its owner's library.
Put target permanent with converted mana cost 4 or more on top of its owner's library.
Idea Snatch UB
Instant
Each opponent reveals his or her hand.
You may search your library for a card with the same name as a card revealed this way, put that card into your hand, then shuffle your library.
Draw a card at the beginning of the next end step if you didnt search your library this turn.
~ U
Enchantment
X: Exile up to X cards from the top of your library face down. Put that many cards from the bottom of your library on top in any order. Put the exiled cards at the bottom of your library in any order. Any player may activate this ability. X can't be 0.
Share Knowledge 1U
Enchantment
Instant and sorcery spells you cast cost 2 less to cast.
Whenever you cast an instant or sorcery spell, any of your opponents may copy that spell. Each of those players may choose new targets for his or her copy other than spells you control.
Ob Nixillis' Vengeance B
Instant (R)
Exile target nonblack planeswalker. Its controller loses 3 life.
Compress Knowledge U
Instant (R)
Split second
Counter target spell or ability.
You discard your hand.
Secrets of the Bandit 1UU
Sorcery (R)
Each opponent exiles the top card of his or her library. You may cast a nonland card exiled this way without paying its mana cost.
Whenever your commander deals combat damage to a player, you may return Secrets of the Bandit from your graveyard to your hand.
Blitz Frost U
Instant (R)
Blitz Frost deals 1 damage to target creature or player. If a creature is dealt damage this way, tap that creature unless its controller pays 2. If a player is dealt damage this way, that player can't cast creature spells this turn unless he or she pays 2.
Trying to Catch Up 5G
Sorcery (U)
If an opponent controls three or more permanents that can be tapped for mana than you, you may pay G rather than pay Trying to Catch Up's mana cost.
Search your library for up to three basic Forest cards and put them onto the battlefield tapped, then shuffle your library.
Astarot, Hell Plunger 3BB
Legendary Creature - Demon (M)
Flash
Flying
Whenever Astarot, Hell Plunger enters or leaves the battlefield, exile target card from an opponent's graveyard. If you do, you may search your library for a card with the same name as that card, reveal it, put it into your hand, then shuffle your library.
4/4
Unwanted Visitor B
Creature - Zombie (R)
Unwanted Visitor enters the battlefield tapped.
Unwanted Visitor doesn't untap during your untap step.
Whenever a nonbasic land enters the battlefield under an opponent's control, untap Unwanted Visitor.
3/3
Unwary Decisions 1B
Instant (U)
Draw three cards, then reveal your hand. An opponent chooses a card from among them. You discard that card.
Spirit Coliseum
Land (C)
t: Add U or W to your mana pool. Activate this ability only if your commander's color has blue and white.
Creature - Vampire Wizard (R)
As an additional cost to cast Cunning Vampire, sacrifice a creature.
Flying
When Cunning Vampire enters the battlefield, if the sacrificed creature deals combat damage to a player this turn, that player sacrifices a permanent.
3/2
Thirteenth Hour 1B
Sorcery (R)
Each player sacrifices a permanent and loses 1 life. If your life total or number of permanents you control is exactly 13, take an extra turn after this one.
Fake Gallery 3UU
Instant (R)
If its your turn, Fake Gallery cost 5 more to cast.
Put a token onto the battlefield that's a copy of each nontoken, nonland permanent each of your opponent controls. Exile them at the beginning of the next end step.