Agitator Ant Army Ants Barbed Shocker Biotech Specialist Cavern Crawler Clickslither Dragonfly Swarm Duct Crawler Evendo Brushrazer Fire Ants Firefly Flameborn Viron Giant Ambush Beetle Giant Solifuge Highspire Mantis Invader Parasite Krenko's Buzzcrusher Lithophage Monstrous Carabid Plated Geopede Robber Fly Shocker Skin Shedder Skyclave Geopede Smelted Chargebug Szarel, Genesis Shepherd Tunneling Geopede Xira Arien Xira, the Golden Sting
Each unit has a Charge Time meter, which is reset to zero after it acts (unless it uses the Wait command, in which case it is reset to 20), and it may only act again after it goes back to 100
A single well-timed board wipe can easily set this deck back to the stone age with no discernable draw engine to speak of
Vraska, Betrayals Sting Proliferate as a loyalty ability is already an engine in and of itself, and Vraska, Betrayal's Sting offers much more than that
It is very convenient for general storage or transportation
This is at instant speed so you can do it to dig and find an answer, unlike most of these effects