Thalias, Imbuer of Life

When Thalias, Imbuer of Life enters the battlefield, up to X other target artifacts you
control become Construct creatures with base
power and toughness equal to X in addition to
their types.
{2}: Return Thalias, Imbuer of Life to your hand
from the battlefield. Only the player who owns Thalias, Imbuer of Life may activate this ability
and only once per turn.