Sivulak, the Primal Veil

As Sivulak enters the battlefield, it becomes your choice of a 5/3 creature with "Creatures with toughness 5 or greater can't block" or a 3/5
creature with "Creatures with power 5 or greater
can't attack."
Whenever a nonbasic land enters the battlefield,
you may pay {2}{u}. If you do, create a blue Shapeshifter creature token with power and toughness equal to the power and toughness not
chosen for Sivulak.