[bq="Background Pony #B46E"]I think that with reminder text, Imprint would end up taking more space than it saved. Also I think it might work better without Imprint from a flavor perspective, but I'm not sure; I'm no expert.[/bq]With the advent of the "exile" term, imprint's been made into an ability word. It'd probably go something like this:
_Imprint_ — When Music Box Assistant enters the battlefield, you may exile a creature you control until Music Box Assistant leaves the battlefield.
Music Box Assistant has all abilities of the exiled card.
Heck, it doesn't even need the ability word.
"@Phil Srobeighn":/1442855#comment_6150783
[bq="Phil Srobeighn"]Making it X ^U^ ~R~ works well, thanks.[/bq]No. No it does not. You are giving _blue_ a _board wipe_ that can _hit players_ and can easily lead to death by "Slither Blade.":http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=426773 Remember, outside of Commander, a hybrid spell can be cast by either color, and thus needs to be an effect that either can do on its own. Blue most definitely can't nuke the field, even if it's a nonlethal variant.
Also, Festering March isn't the right comparison here, since the worst-case scenario is it applying only during one player's turn. Think more along the lines of "Night of Souls' Betrayal,":http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=78991 "Curse of Death's Hold,":http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=227075 or "Phyrexian Lady Gaga.":http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=397880