Is it possible for the attacker to loot the defender minerals if they won? Or the only way to gain is by conquer and tax only?

Im asking because i may be gone for few days so wondering if during that mean time others can loot my minerals~

If you mean when someone else attacks you and wins, they take all your resources, no. Even if you get conquered you don't really "pay tax", even though your conquer will get taxation. So you don't lose any res at all, unless you got spy attacked, ofc... but that res goes to no one.

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It goes to the owner of the op

I think you're talking about salvage...

it won't affect you any way. you will just lose units in battle.. and crystals.. that's a big lose. no affect on resources,