Are all events one-shot?
All events are one shot and the "Monster" in the card is mainly flavor text to make it fit into the game more without just being a random mechanic.

Think of it this way, if the card removed the text would it take away from the game for you?


  You man discard this card and an item. If you do not the player to the right rolls a might attack of 4 against you defend with might as normal. If you take damage from this attack take the top 3 cards from the event deck and shuffle this back in.


In general event cards will inform you when they impact the game board in a long term fashion by instructing you to place tokens on the board.