You can unlock this on any level with a Crow Shrine, in any game mode. The easiest method is to create a local game with two players on the Chaos Canyon map, with unlimited time and 100 rice. Note which color is your primary profile and with one of its units haunt the Crow Shrine which is at the very center of the map. This will spawn a Crow Monk on the following turn. Kill three of your secondary profile's units and have the Crow Monk eat their skulls so that he becomes a Demon Crow Monk. On your secondary profile's turn, line three of your units up right next to each other on the edge of the cliff that makes up the bottom of the map. Select the Demon Crow Monk and move within range of the three units on the cliff edge, choose Spell, and select Typhoon which will be the spell all the way to the right. Target the middle unit, confirm the spell and all three will be knocked off the edge of the cliff, unlocking the achievement.
I recommend doing this achievement at the same time as "Epic Win" to save yourself time killing all the units that have to be created for that achievement. Note that doing so requires creating a pass and play or online game, rather than local as detailed at the beginning of the guide for this achievement.