After turning the corner to get to Room 13, you continue on. All doors are on the right-hand side of this hallway.
Inside room 14 is a human male looking over another portal. On the other side of the portal is a dungeon room that looks very similar to the one they are currently in.
The man, a Warlock, will speak to the characters in a language they do not understand. After a few tries of failing to communicate, he will blast what he believes to be the wizard with an Eldritch Blast. He has to roll to hit (THAC0: 19), and it causes 1d6+2 points of damage. He can do this every round. He has AC 9 and 11 hp.
There is a 30% chance he has a magic item suitable for a wizard/magic-user.
The portal leads to another world that looks exactly like the one they have left, and they might not even realize they have gone anywhere. The world is the same, but the rules here use the Dungeons & Dragons 4th Edition rules. Tell the players to give you back their sheets and hand them the same characters for the 4th Edition version of the game.
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This monster for this room was inspired by the old Monster & Treasure assortment for the Second level.
I figure if he was a warlock, then he might as well be a 4th Edition one!