How to beat Icy Room in Find Mii II

The second time I played through Find Mii II the Castle of Darkness - Courtyard room was frosty when I first entered it.  To make it no longer an icy room and reveal the enemies, just send in two red heroes in a row.  They will automatically team up and thaw out the room.  This is a permanent change, so no need to have enough heroes to beat the room right away.  Note that one of the enemies can scare away a hero and the other uses barrier gas, so you might want to waste/low level heroes in front of any high level heroes.