During our demo, Rosewater repeatedly talked through his game plan the same way a Magic player might narrate a Commander game, not quite with an open hand, but for claritys sake, as he weighed whether he should destroy one of my higher-value cards immediately or set up a larger combo a turn later
If you somehow control Barrensteppe Siege and no choice was made for it (perhaps because another permanent on the battlefield became a copy of it), it has neither of the two abilities
Granted, you get a creature token on top, but assuming an average top five reveal, thatll be a 2/2 or a 3/3, and Im not entirely sure thats worth the extra mana cost
As it makes 2 per attack you will accumulate them faster even through some defenses
On turn three, you dont even need a land, because you can use her ability to copy the mana dork and then play the Guardian