Given the number of Treasure tokens taking over Commander, every time a player wants to spend mana, you can start pinging their life down with Mayhem Devil
It's high value on the secondary market is due to Atraxa and other new cards in her deck like Deepglow Skate
At common, creatures like Mechan Shieldmate and Cloudsculpt Technician grow stronger when you play or control artifacts, but thats true for every blue deck
A 4-mana 4/4 with Vigilance is a great starting point, and this has upside that is very useful in this format
The game starts as neither
PrintMTGs proxy/playtest cards are designed around that in-sleeve consistency idea: standard MTG sizing, familiar feel, and predictable finishing so your deck doesnt end up with one card that behaves like its trying to get caught