By the way, you can avoid copypasting the Soulshift reminder text everywhere by defining a mechanic. Then you'd just need to write [Soulshift] and it'd expand it automatically. This is especially useful if you might want to make changes to the reminder text (or mechanic name), because it'll be applied automatically to all cards with that mechanic.

Making soulshift get back any dead Spirit, not just one with a smaller CMC, seems worrying. Letting it get back Arcane cards as well seems frankly broken. Do you have Glacial Ray or Rend Flesh in the set? Getting one of those back whenever half of your creatures die seems way too strong. (Unless you're either cranking up the costs on the Arcane cards a lot, which you don't seem to be doing, or reducing the number of soulshift cards, which you seem to be doing the opposite of given that the original Tallowisp didn't have soulshift.)

Mmm.. soulshift was always annoyingly weak, and hard to get to actually work; though.

You reckon? I found it very powerful in Kamigawa-block limited. Such incredible card advantage. Best if you had a Thief of Hope, of course, or if they could pop themselves like Scuttling Death, or if you had a Death Denied or Soulless Revival to restart the chain once you topped it out... but it could be pretty powerful.