That means, if you deck qualifies to have a companion, it would be considered card #101
So yes, its about 5-10 times easier to get a nonfoil, and 2-3 times easier to get a foil, depending on if the card would be rare or uncommon
Effects that modify a creature's power and/or toughness, such as the one created by Blazing Crescendo or a +1/+1 counter, will apply to the creature no matter when they started to take effect
In the video, we see what looks to be a Saga titled the Horus Heresy, for instance (anyone familiar with the 54-book Horus Heresy series will know that's an apt name for it), and Warhammer versions of existing Magic cards make their appearance too
Ingest is an interesting ability, snatching cards from the top of opponents' libraries and sending them to exile