Hired Giant

When Hired Giant enters, each other player may search their library for a land card and put that card onto the battlefield. Then each player who searched their library this way shuffles.

Eager Construct

When Eager Construct enters, each player may scry 1. (To scry 1, look at the top card of your library, then you may put that card on the bottom.)

Myr Custodian

When Myr Custodian enters, scry 2. Then each opponent may scry 1. (To scry X, a player looks at the top X cards of their library, then puts any number of them on the bottom and the rest on top in any order.)

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.

Boldwyr Heavyweights

Trample
When Boldwyr Heavyweights enters, each opponent may search their library for a creature card and put it onto the battlefield. Then each player who searched their library this way shuffles.