what do you do when you get to Merlin?

I am assuming you mean what to do when you start the level? You need to pick up the TNT barrels inside the fence area and use them open all of the locked doors. You can either hold them in your hand and ignite them off of the headless fire soldiers and throw it at the door or set it down in front of the door and the soldier will set it off eventually if you are anywhere near the door. You need to do this for each door and it is difficult to keep the soldiers away from you because they fire flame arrows at you. Let me know if this helps.

I was wondering about the merlin too, I havent passed all the boards yet, we got 34 of 37 so far, but when we did the board with the fishes and the dragons (cant remember the name) we saw a red merlin there in the moat. When you try to jump to him he dissapears. What is he for?? Are you supposed to do something?? Is it possible to catch him, and we are jumping up there too slow? Carmen