Mirrorworks

Whenever another nontoken artifact you control enters, you may pay {2}. If you do, create a token that's a copy of that artifact.

Sarinth Steelseeker

Whenever an artifact you control enters, look at the top card of your library. If it's a land card, you may reveal it and put it into your hand. If you don't put the card into your hand, you may put it into your graveyard.

Hollowmurk Siege

As this enchantment enters, choose Sultai or Abzan.
• Sultai — Whenever a counter is put on a creature you control, draw a card. This ability triggers only once each turn.
• Abzan — Whenever you attack, put a +1/+1 counter on target attacking creature. It gains menace until end of turn.

Hardened Scales

If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on it instead.

Inspiring Statuary

Nonartifact spells you cast have improvise. (Your artifacts can help cast those spells. Each artifact you tap after you're done activating mana abilities pays for {1}.)

Mandate of Abaddon

Choose target creature you control. Destroy all creatures with power less than that creature's power.

Power Fist

Equipped creature has trample and "Whenever this creature deals combat damage to a player, put that many +1/+1 counters on it."
Equip {2}

Coming Attraction

Search your library for a basic land card, put it onto the battlefield tapped, then shuffle. Open an Attraction. (Put the top card of your Attraction deck onto the battlefield.)

Cranial Plating

Equipped creature gets +1/+0 for each artifact you control.
{B}{B}: Attach this Equipment to target creature you control.
Equip {1}

Elvish Archivist

Whenever one or more artifacts you control enter, put two +1/+1 counters on this creature. This ability triggers only once each turn.
Whenever one or more enchantments you control enter, draw a card. This ability triggers only once each turn.

The Most Dangerous Gamer

Deathtouch
Whenever The Most Dangerous Gamer enters or attacks, open an Attraction.
Whenever you open an Attraction, put a +1/+1 counter on The Most Dangerous Gamer.
Whenever you claim the prize of an Attraction, destroy target permanent.