Last night, while trying out the expansions for Boss Monster, my opponent triggered Lady Vix's Level Up ability and stole my Cheat Code. However, she already had a face-up card that she wanted to keep face-up (she mainly wanted to take Cheat Code from me, not use it for herself). This is where a discrepancy came up.
According to Lady Vix's Level Up, she must take a face-up Item Card and place it face-up in her scorekeeping area, but there is nothing explicitly stating that she is able to have two Item Cards face-up as a result. In contrast, the additional Boss monster for the Alien Artifact treasure in this expansion has a Level Up that explicitly states he is able to have two face-up Item Cards for the remainder of the game, so this seems like an ability unique to him.
Level Up: Take a face-up Item from a Hero in town or another player. Place it face up in your scorekeeping area.
When Lady Vix's Level Up is triggered and the player is forced to take an Item Card, is the player also forced to turn their existing face-up Item Card face down to make room for the stolen Item Card? Or is the player able to use two Item Cards during that turn?