Grog-Gnog isn't terribly fancy or strategic, he just enjoys snow days and smashing things. So it shouldn't come as a surprise that his epic is very straight forward, it lets him smash even MORE things!
Gift of the Avalanche increases Grog-Gnog's skill, defense, and max health, and also gives him a chance to do 3 additional attacks on random enemies, and that's in addition to his normal 2 hits for a total of 5! BAM! BAM! BAM! BAM! BAM!