Fetch Lands have been reprinted. They are great for this deck.
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If Springleaf drum is only used for shrapnel blast, why don't you use Astral Cornucopia, and just cast it for 0?
It depends on how aggressive you play the deck. In its current state, I would leave in Drown in Sorrow and just side in ulcerate if you are getting overwhelmed too early.
Ulcerate will be very relevant, you should sideboard it in.
How about Time Warp on a Panoptic Mirror?
I'm really going for her +1 and 0 ability, The plus one is for later game if I cant get the power to overrun them, its more directed for the later game like Doom Engine, Soul Of New Phyrexia, and Stormbreath Dragon. The 0 ability is for speeding up the game if the deck stalls, because it combos well with Ornithopter and Shrapnel Blast. I really don't see my using her -7 except for a last resort. I would have run 2 but the +1 goes well with more than 2.
I think that works pretty good, I wouldn't have put in the unicorn, but there are no other good artifact creatures and 4 Revokers seems excessive.
Sweet! Seems like a very good deck, I may take that into consideration with mine :)
Okay, what should I switch for it? and How many?
Seems good, I would worry about your substance for early game. Also, putting just one copy of a card into a deck is not great, you may want to reconsider that.