Thanks, this was extremely helpful in better understanding the relationship between the two. I had missed this.
No probs!
I read the transcript of your game - pretty cool.
Thanks!
Was the roper introduced due to the Action Declaration of the player or due to the success with the Perception check?
Or in other words, what would have happened if the player had rolled poorly - would the roper have been introduced?
That's an excellent question, but I can't recall properly. At the time I must have had something in mind, but I don't know what I would have done - maybe a surprise attack from the roper?
I think I was using the Monster Vault (as opposed to a hardcover MM), and I have the vaguest of memories of looking at the Perception DC to notice the roper, so that suggests the roper was on my mind
after the action declaration (looking at the stalagmites) but
before the roll was actually made.
And did you actually say something to the effect of "I had not prepared for a roper, but your action declaration/perception roll prompted be to include it" ?
Something more colourful than that, but more or less. The table was in
no doubt as to what had happened - the player in question had thought of the possibility that there might be a roper disguised as a stalagmite, and I had been prompted to look up my book (as above, I think in the context of calling for a Perception check) and then narrated the roper. When my friend was reminiscing about it a few weeks ago, he was the one who was laughing at it being the (other) player's fault, as it was the (other) player who had introduced the possibility by declaring the action.
My view is that in classic D&D that sort of GMing would be outrageous hosing of the players; but in 4e it actually makes for a more fun game - the players can see the GM upping the stakes, and can make their decisions in response, and 4e players have a remarkable depth of resources to respond with
and the recovery of resources is linked in part to the XP-weight of an encounter (via the milestone system).