All this logic of "this event isn't free because you need to own Rise of Iron" is incredibly flawed. By this type of thinking, nothing in this world can ever be free. If your local pizza place put out an add stating "free pepperoni pizza" and you got there, and on the window is a sign that reads "no shirt, no shoes, no service", would you yell at the owner because you had to buy a shirt and shoes in order to get this pizza? Yes, in order to participate in this seasonal event (which by the way, lots and lots of other game companies add free seasonal events to their games) you need to own the latest expansion. If you didn't already own this expansion, I very highly doubt that this event would cause you to want to buy it. If it did, then yes, you're right, to you it isn't free because you had to purchase something before playing it. If you did purchase Rise of Iron in order to play in this event, congratulations, you now get a ton of free bonuses such as new missions, new strikes, a new raid and tons of new gear!