There is no limit on the number of guild keys that can be made available.
Initially, when the guild is purchased, three (3) keys are available. After that. each additional key costs 500 diamonds.
Keys are purchased from an altar within the guild hall. Those keys only work for that guild hall.
The altar "resets" after ~2-hours of RL time. The reset works under the same conditions as any other map reset - no players can access the guild for 2-hours for it to reset. NOTE: any items left on top of the altar will disappear when the map resets; basically, the "square" that the altar sites on is *not* a unique map tile - the rest of the guild is and that is why items are not lost in map resets.
In order for the front gate to open in the guild hall, you'll need the key in your inventory.
If there are any more questions in regards to guild hall keys, please post to this thread so they can be addressed.
Thanks.
