Flight of Icebirds

At the beginning of your upkeep, put a snowflake counter on Flight of the Icebird.
{1}{u}{u}{u}: Tap target creature and put a
snowflake counter on Flight of the Icebird.
Remove X snowflake counters from Flight
of the Icebird: Create a blue X/X Icebird
creature token with flying. Then, if X is four
or more, tap all creatures.