A lot of people feeling like Sweetfeather needs a little buff but I can’t see it. Dreamy entrance then gets a turn faster than most of the other sleep monsters and will instantly put a second monster to sleep on the first turn before using exit plan so you have a 4v2 for the next ~300s (Soulstealer and the like are faster). The restriction is you’ve got to have link set up but it’s worth it for the pay-off and you only need it for the first time it comes in. If it gets killed before its turn then you still got the benefit of an enemy monster asleep for 320s.
It can also work as a sweeper alongside other sleep monsters but the main use I reckon is dropping in and out of play putting enemy monsters to sleep.
There was a thread recently which discussed it: Swetfeather