Uncanny X-Men (1st series) #143

(flashback)

Storm battles N’garai demons that try to invade Earth through a cairn near Xavier’s mansion. At first she is able to avoid their attacks, but finally she is hit by a bolt of energy and drawn inside the cairn. Being claustrophobic she panics and shatters the cairn with a flash of lightning. Believing the threat to be over, Storm returns to the mansion. The seasons turn and their battle with the N’garai is all but forgotten, but far from over. Professor Xavier believed that destroying the cairn would forever seal this gateway between the N’garai dimension and Earth. He was wrong as over a year later one of the demons crawls out of the debris. A young couple is out in the woods to get themselves a christmas tree, they are only the first to be attacked and killed by the demon.
(present)

Christmas Eve in the Mansion. Kitty's getting a lesson on flying the Blackbird from Professor X. Angel comes in to tell him that his car is ready. Talk about a timely interruption, Kitty jokes. She feels like she could build the Blackbird out of spare parts with her eyes closed by now. He won’t be satisfied until she can, Xavier deadpans. Angel comforts her that they all had to go through this. Now it’s her turn and this is just the easy part. He’s sure Kitty appreciates such encouragement, Xavier comments wryly and adds that he’ll be downstairs directly.