Sublime Exhalation

Undaunted (This spell costs {1} less to cast for each opponent.)
Destroy all creatures.

Black Sun's Zenith

Put X -1/-1 counters on each creature. Shuffle Black Sun's Zenith into its owner's library.

Ancient Stone Idol

Flash
This spell costs {1} less to cast for each attacking creature.
Trample
When Ancient Stone Idol dies, create a 6/12 colorless Construct artifact creature token with trample.

Bellowing Fiend

Flying
Whenever Bellowing Fiend deals damage to a creature, Bellowing Fiend deals 3 damage to that creature's controller and 3 damage to you.

Reaver Titan

Void Shields — Protection from mana value 3 or less
Gatling Blaster — Whenever Reaver Titan attacks, it deals 5 damage to each opponent.
Crew 4 (Tap any number of creatures you control with total power 4 or more: This Vehicle becomes an artifact creature until end of turn.)

Walking Skyscraper

This spell costs {1} less to cast for each modified creature you control. (Equipment, Auras you control, and counters are modifications.)
Trample
Walking Skyscraper has hexproof as long as it's untapped. (It can't be the target of spells or abilities your opponents control.)

Barricade Breaker

Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)
Barricade Breaker attacks each combat if able.