How does this card work? Do I have to pay any costs if I play a card from an opponent's discard pile? If it's a character, do I control it till the end of the phase or permanent? Please clarify what is the use of this card.

"While you control only GJ characters and locations, you may play the top card of one opponent's discard pile as though it were in your hand (Limit once per round)."

Playing a card as if it were in your hand means exactly that: if you decide you want to play it, you pretend that it's in your hand. So yeah, you have to pay all costs (including out-of-House penalties) and follow all applicable timing rules. But like a character, location or attachment played from your hand, it stays in play - under your control - until specifically removed.

Note that this only works for playing cards. You could not, for example, use a "put into play" effect on a card that is on top of your opponent's discard pile (like, say, Ambush on a Targ card).

I think that the location is not worth playing because for 5g you can play efectively only opponent Events (asuming they dont have a House X only restriction), becase if you play anything else (char, location or attachment out of House for +2g) you will not be able to use the Ten Towers again since you will have a non-GJ card now.

Rozy said:

Once the game starts, "House X only" doesn't mean anything. It is a deckbuilding restriction only, meaning that the card cannot be built into a deck other than the stated House. Once the game starts, it's the same as any other card.

"House X only" does not stop an opponent with a different House from taking control of the card or triggering the effect once the game starts, assuming it is owned by and brought to the game in a deck played by someone with the appropriate House card. So Ten Towers does indeed let you use events (or characters/locations/attachments) from an opponent's discard pile with a "House X only" restriction.

I was actually reminded of and intrigued by Ten Towers while I was looking into a GJ charlite/less deck. I'm still toying around with the idea especially with threat from the north and valar D as more options for discarding cards in play.

Yeah, but for 5 gold in my Greyjoy deck, I just don't want to dedicate the resources to this card. I can usually do much more with 5 gold. Back before ccg rotation there were several ways to get this card into play for free, and it was in my deck at that time (King Balon's Command being my favorite).