Those Keys will set your "spawnpoint" when you jump into the well you will end up at the Underbelly Inn.

Sold by 柯胡塔 in the Underbelly at 65.6 | 80.0

That key opens a portal in Underbelly (Dalaran) which you can use to port yourself to another opened portal.
传送门钥匙：废弃小屋 (43.38, 52.75)
传送门钥匙：炼金师之巢 (78.73, 78.80)
传送门钥匙：黑市 (70.08, 15.15)
传送门钥匙：旅店入口 (68.18, 67.32)
传送门钥匙：下水道卫兵岗哨 (69.00, 55.80)
传送门钥匙：后门 (31.42, 45.99)

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传送门钥匙：旅店入口

物品等级：1
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[Vendor Locations]

[This item can be purchased in] 达拉然（3）.