Drossforge Bridge

This land enters tapped.
Indestructible
{T}: Add {B} or {R}.

Razortide Bridge

This land enters tapped.
Indestructible
{T}: Add {W} or {U}.

Goldmire Bridge

This land enters tapped.
Indestructible
{T}: Add {W} or {B}.

Slagwoods Bridge

This land enters tapped.
Indestructible
{T}: Add {R} or {G}.

Darkmoss Bridge

This land enters tapped.
Indestructible
{T}: Add {B} or {G}.

Ob Nixilis, Unshackled

Flying, trample
Whenever an opponent searches their library, that player sacrifices a creature of their choice and loses 10 life.
Whenever another creature dies, put a +1/+1 counter on Ob Nixilis.

Mistvault Bridge

This land enters tapped.
Indestructible
{T}: Add {U} or {B}.

Niv-Mizzet Reborn

Flying
When Niv-Mizzet enters, reveal the top ten cards of your library. For each color pair, choose a card that's exactly those colors from among them. Put the chosen cards into your hand and the rest on the bottom of your library in a random order.

Wan Shi Tong, Librarian

Flash
Flying, vigilance
When Wan Shi Tong enters, put X +1/+1 counters on him. Then draw half X cards, rounded down.
Whenever an opponent searches their library, put a +1/+1 counter on Wan Shi Tong and draw a card.

Opposition Agent

Flash
You control your opponents while they're searching their libraries.
While an opponent is searching their library, they exile each card they find. You may play those cards for as long as they remain exiled, and you may spend mana as though it were mana of any color to cast them.

River Song

Meet in Reverse — You draw cards from the bottom of your library rather than the top.
Spoilers — Whenever an opponent scries, surveils, or searches their library, put a +1/+1 counter on River Song. Then River Song deals damage to that player equal to its power.

Archivist of Oghma

Flash
Whenever an opponent searches their library, you gain 1 life and draw a card.