you need the expansion pack for the shield BUT you can get the cloak of mirroring during the regular game... just equip one fighter with it and go to a beholder's layer then viola... instant level up (believe me)
spoiler:
you can only get the cloak of refelction shield after the spellhold (chap4 i think) going to the underdark (chap5) by ship (its in the sahugen city)
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