The portals in Aleroth only produce creatures until Zandalor has time to seal them, so you need to let enough past to keep interrupting his spell. You may want to turn the sound down for that, as he complains each time he is attacked and needs to restart. The main floor would be easiest for this, since there are 3 portals there.
In Keara's fortress, in the initial section of the headquarters, opponents spawn each time you try the door to the inner headquarters, if you have not named all of the statues correctly (or not named any yet).
