Tome of Constructs

When Tome of Constructs enters the battlefield
you may discard a card. If you do, draw a card.
Whenever you discard a card, exile that card
from your graveyard with a catalog counter on it.
{3}{r},{t}: Create a token that's a copy of target creature you own in exile with a catalog counter
on it, except it has haste and "At the beginning
of the end step, exile this permanent."