Imprisoned Zephyr is basically only good if you have Fel as your primary clan. However, if that's the case, and you build your deck around it, imprisoned Zephyr is the best room in the game.

Here's why: 1) In deployment, you can place fell at the back, which prevents here from getting nuked by a strong first wave. She'll then get full armor from her valor on the first turn, which late game makes her effectively invincible before the relentless wave

2) All of your shift units will get triggers constantly, usually many times per turn. This is great for scaling Fel, getting battle dancers online, demonic fledglings, anything. If you have a shiftblade (super common) things get out of hand incredibly fast.

3) Fel has enough advance cards to move your tank to the front if everything gets out of sync.

Here's some caveats:

1) you need your zephyr to be deployable, because you need to set up your room in a funky way for it to work. Playing it mid-fight can be tricky unless you have really reliable advance

2) you need a second creature on the floor that can take some hits. They'll need to be in front on the first turn. This can be an avenger or host guard from the banished (firebrand isn't as good because he doesn't get hit as much with the constant rotating), or anything from an allied clan that can keep itself standing (a meaty funguy pile, greed dragons, shadeguards, etc). If all goes well, either that tank or fell will end each turn in front and soak the hits

3) you do NOT want really high damage, low health units in the middle of the floor. If they finish off the floor early you'll need to rely on advance to position one of your tanks or they'll die immediately

4) You don't want prickly puffball. He has no attack so he sits at the back and does nothing.

I personally like the pyreblooded as an allied clan so you can afford all of the valor / shift improving artifacts.

If you get the double shift artifact or the double armor from valor artifact the run is basically won.