Thyr, apocryphal messiah

+2: create a 7/7 with flying,trample and,every turn this creature adds +3/+3
-8: Thyr, apocryphal messiah turns into a 15/15 with flying and with,every turn Thyr, apocryphal messiah doubles its power and toughness.
-12: double your life total every turn, unless your opponent has two forests,two swamps and two planes.