Cards with goad or other ways to give your creatures evasion are useful in Commander to help facilitate such strategies
Still, if you're running a casual game, then this should be fair game
I especially like how much control you have over when this transforms because it only triggers off spells that cost 4 or more, or you can put counters on the Emperor so you just need to trigger it once or twice to flip
Especially in the Commander format, blink-focused strategies helmed by commanders like Brago, King Eternal are remarkably popular and powerful
That includes other equipment, traditional artifacts, and artifact creatures
On September 14, Wizards of the Coast revealed a full deck list for its second MTG Warhammer 40k crossover Commander deck, The Ruinous Powers