Original card based on a location mentioned only in the Homelands comic. There are only two sentences in MTGSalvation on the Dwarven Gate, so I'm just going to copy/paste them here:

"The Dwarven Gate was a planar portal beneath Castle Sengir that led from Ulgrotha to an unknown plane. Baron Sengir wished to conquer Ulgrotha, then march his troops through the portal to take whatever was on the other side."

I tried to give this flavor of 'first my kingdom, then yours'. It's probably not a perfect match, but I like how defensive and aggressive decks would use it in different ways, so I'm cool with it.

You should only be able to activate this during your declare attack step. Right now, you can get bonus attackers after blocks have been declared, or worse, attack on an opponent's turn. That's too wonky.

You can't use this to attack on another player's turn - the last clause says they only enter attacking if it's your turn.

This is a bit hard to balance. It probably does need to be able this expensive, because putting multiple things OTB attacking for free is very strong, but it's a pity it's so unpredictable.

It's a bit less good on defence, because people can see it coming, and choose to only attack with one or two creatures.

I wonder if rather than sacrifice, it could be something like ", : Exile the top card of target player's library. If it's a creature card, you may put it onto the battlefield under your control. If it's your declare attackers step, it enters the battlefield tapped and attacking."

(It's probably a bad idea to get free attackers /after/ the opponent has had any chance to declare blockers.)

Whoops, missed the "your turn" part. A general timing restriction would probably clean up the template, though.

@Dude: Mmm, true. They shouldn't be unblockable. Highlighting for later change.

@Alex: I want this to be explosive, but I agree. Whiffs are annoying. Maybe I can rewrite this so you don't have to sacrifice it unless you like the cards that were exiled (Kind of Like Petals of Insight). It would start becoming a strong way to mill someone... but at , I don't think that's a problem.

Oh, and if your opponent has an army, but elects to only swing with one creature because this is active, then it's kind of doing its job. Admittedly, that's not very exciting. But the exciting mode is on the attack anyway.

Alternatively, I guess this could not sacrifice, Exile X, then choose one. Not what I was going for, but would make for a solid card.

Alright, dropped to 'Exile X, choose one' and added before blocking restriction. The card ended up a little better for control decks, and little more challenging for rush decks to take advantage of. Oh well. Looks like a decent card, though.