A Frosty Creature
A mysterious Pokémon has recently been seen in Emera Town. It's said to cover everything in its surroundings in frozen ice.
The Frosty Creature is a Kyurem. This event started the 4th of December and ended on the 19th of March 2014.
Kyurem was then once again obtainable from the 6th of January 2015.
Obtaining Kyurem
Kyurem can be obtained by interacting with Eggs & Pokemon. An icon of Kyurem will randomly appear on your userbar while interacting. If you see the icon, you can click on it to get the egg, provided you have a free space in your party to obtain the egg, but if you don't, you always have time to make space. Note that it is not required to ave a free slot in the party for it to appear in the userbar.
Receiving Kyurem
After clicking the Kyurem on your userbar, it will show you a clearer image of it, and will ask you if you want to claim the gift.
After accepting the creature's gift, you will have a Kyurem Egg in your party.