I was thinking of a context as for example one saying to another "listen, because I have a weapon which injures, and because it injures it causes pain, beware".

This is not a grammatical sentence in English. You've got a subordinate clause because I have a weapon which injures. Then you're and-ing it with another subordinate clause, because it injures. Note that because it injures it causes pain is not a subordinate clause: it is a subordinate clause (because it injures) and an independent clause (it causes pain). Then you have the independent clause, beware.

I think what you have here is your usual habit of splicing sentences inside sentences. It just doesn't work here.

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SuStel
http://trimboli.name