Boros Signet

Smothering Tithe

Whenever an opponent draws a card, that player may pay {2}. If the player doesn't, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Land Tax

At the beginning of your upkeep, if an opponent controls more lands than you, you may search your library for up to three basic land cards, reveal them, put them into your hand, then shuffle.

Wayfarer's Bauble

{2}, {T}, Sacrifice this artifact: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Esper Sentinel

Whenever an opponent casts their first noncreature spell each turn, draw a card unless that player pays {X}, where X is this creature's power.

Burnished Hart

{3}, Sacrifice this creature: Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

Mind's Eye

Whenever an opponent draws a card, you may pay {1}. If you do, draw a card.

Rakdos Signet

Sol Ring

Dark Ritual

Ornithopter of Paradise

Insatiable Avarice

Spree (Choose one or more additional costs.)
+ {2} — Search your library for a card, then shuffle and put that card on top.
+ {B}{B} — Target player draws three cards and loses 3 life.

Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

Syphon Mind

Each other player discards a card. You draw a card for each card discarded this way.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Phyrexian Arena

At the beginning of your upkeep, you draw a card and you lose 1 life.

Kaalia of the Vast

Flying
Whenever Kaalia attacks an opponent, you may put an Angel, Demon, or Dragon creature card from your hand onto the battlefield tapped and attacking that opponent.