Good morning ,
I have two questions related to the Descent 2 "Heirs of Blood" campaign, specifically the mission The Mountain of ShadowFall:

1: In the same turn, can OL summon Kadlasar on the map and at the same time remove him if the lair has not yet been discovered?

2: If Kadlasar defeats a hero, but another hero uses a specific ability that says "If a 3-space hero is about to knocked out, exhaust this card to make him recover X", the OL takes the token anyway. or not ? The OL draw a card ?

1 - As the rules are written, yes, but I assume that the word "already" is missing.
So, I understand it as "At start of the Overlord's turn, if Kadlasar is not on the map, place him ..." and " At start of Overlord's turn, if Kadlasar is already on the map, remove it from the map ..."

2 - No, if the hero is not defeated, because saved by any skill or ability, then the KO rules does not occur