I've just started Diablo 2 in single player mode, and there is one thing I don't understand.

Some opponents drop keys, generally in multiple numbers (like 6 of them stacked). I can buy them in the towns, too. They seem to be generic, and don't have to be identified, so no mystery there.

What do they open?

Can I sell them without worrying about that they might be useful later?

2 Answers

Keys are used to unlock locked chests, which are scattered across the game world. As per this page:

Keys are dropped by monsters or purchased for a very low price in town. They stack 12 high, and are readily available. Each time you open a locked chest, one of your keys is used, and destroyed. There are no locked doors, and never anything in a locked chest you have to have to advance in the game. They are purely a bonus item, but as locked chests are common, you should be sure to always carry some of these (unless you play an Assassin, who can pick locks).

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It is about those three keys that you can only use them în hell mode on level 5 Harrogath

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