Previous Versions can be found here.
Whimsalot is essentially the upgraded version of Whimsun, much like it is in Undertale hard mode.
Whimsalot will reduce the cost and stats of all monsters in your hand by 1, down to a minimum of 1/1. This can be good for cards that have valuable effects rather than stats.
Strategy[]
Whimsalot can be used to cheapen the cost of cards that don't rely on their stats to gain value. Additionally, it has great synergy with self-silencing cards such as Ball Person and Action Figures due to the fact that it nullifies the stat decrease.