uba mask/ sylvan library

[Juggernaut GO]

I know that uba mask will remove the 2 cards u draw from the game with sylvan library, but....what happens when u cant put the cards back?  do you lose the 4 life for each of the 2 additional cards you draw or just nothing happens?

also, what happens when you have more then 1 sylvan library in play,  say you have 2 sylvan in play :  you trigger the first, draw 2 extra cards, they get removed, you trigger the 2nd, you draw 2 more extra cards, they get removed....Does this work?

[Komatteru]

ylvan's oracle text reads:

At the beginning of your draw step, you may draw two cards. If you do, choose two cards in your hand drawn this turn. For each of those cards, pay 4 life or put the card on top of your library.

You didn't draw the cards actually.  The draws were replaced.  Thus, you didn't draw 2 extra cards this turn, so you don't have to put anything back.

[Gabethebabe]

also, what happens when you have more then 1 sylvan library in play,  say you have 2 sylvan in play :  you trigger the first, draw 2 extra cards, they get removed, you trigger the 2nd, you draw 2 more extra cards, they get removed....Does this work?

Each Sylvan you have will provide you with two extra cards with Uba Mask in play.

[LotusHead]

also, what happens when you have more then 1 sylvan library in play,  say you have 2 sylvan in play :  you trigger the first, draw 2 extra cards, they get removed, you trigger the 2nd, you draw 2 more extra cards, they get removed....Does this work?

Each Sylvan you have will provide you with two extra cards with Uba Mask in play.

One last thing I need cleared up with Sylvan Library: during draw step is it "draw Card for turn- then Sylvan trigger goes on stack" or is it draw step: "sylvan trigger goes on stack, Draw card for turn, resolve Sylvan trigger?" I have always played the later way, but only with casual Sliver decks and such.  Assume 1 Sylvan Library in play and no Uba Mask.

[Godder]

draw Card for turn- then Sylvan trigger goes on stack

That one - the rules changed, and now the card draw in your Draw Step happens at the beginning of the Draw Step without using the stack, so it can't be responded to (or Stifled, which was the reason for the change). That said, that doesn't really functionally change Sylvan Library, although if you manage to draw other cards this turn e.g. Ancestral during upkeep, you could put two of those back instead.