Walking Ballista

Walking Ballista enters 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.

Rings of Brighthearth

Whenever you activate an ability, if it isn't a mana ability, you may pay {2}. If you do, copy that ability. You may choose new targets for the copy.

Conspiracy Theorist

Whenever Conspiracy Theorist attacks, you may pay {1} and discard a card. If you do, draw a card.
Whenever you discard one or more nonland cards, you may exile one of them from your graveyard. If you do, you may cast it this turn.

Moonsilver Key

{1}, {T}, Sacrifice Moonsilver Key: Search your library for an artifact card with a mana ability or a basic land card, reveal it, put it into your hand, then shuffle.

Containment Construct

Whenever you discard a card, you may exile that card from your graveyard. If you do, you may play that card this turn.

Mishra, Excavation Prodigy

Haste
{1}, {T}, Discard a card: Draw a card.
Whenever you discard one or more artifact cards, add {R}{R}. This ability triggers only once each turn.

Trinisphere

As long as Trinisphere is untapped, each spell that would cost less than three mana to cast costs three mana to cast. (Additional mana in the cost may be paid with any color of mana or colorless mana. For example, a spell that would cost {1}{B} to cast costs {2}{B} to cast instead.)

Portal to Phyrexia

When Portal to Phyrexia enters, each opponent sacrifices three creatures of their choice.
At the beginning of your upkeep, put target creature card from a graveyard onto the battlefield under your control. It's a Phyrexian in addition to its other types.

Mishra's Research Desk

{1}, {T}, Sacrifice Mishra's Research Desk: Exile the top two cards of your library. Choose one of them. Until the end of your next turn, you may play that card.
Unearth {1}{R} ({1}{R}: Return this card from your graveyard to the battlefield. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Imperial Recruiter

When Imperial Recruiter enters, search your library for a creature card with power 2 or less, reveal it, put it into your hand, then shuffle.

Basalt Monolith

Basalt Monolith doesn't untap during your untap step.
{T}: Add {C}{C}{C}.
{3}: Untap Basalt Monolith.