"Okay, Peter, so what's your master plan?" Sirius asked as they raced towards the tree.
"If we can get the top sharp enough and angle it just right, we might be able to use the tree as a spear. One moment." And with that, Peter changed into his Animagi form of Wormtail leaving his clothing behind and proceeded to climb up the tree branches. Once at the top, he changed back and broke through the branches. "Toss me my knife."
"Here, catch." James threw the knife and Peter began to whittle the top of the tree, making it into a sharp point slowly but surely. Outside the doors, they heard howls and roars coming closer.
"Peter, hurry! We're kind of on a deadline here!" James shouted.
"Got it!" Peter replied, before turning to his form as Wormtail, falling through the tree and scurrying back into his discarded clothes. "Wait, my shirt's on backwards. Damn it."
"We can fix it later. Come on. Wingardium Leviosa!" James made the tree hover, slowly titling it to face the tip towards the door. At that moment, the doors flung open, and a ragged and bloody creature was thrown inside. Its body was bruised, and probably broken, and blood covered several parts of its limbs.
"Moony… oh boy." And the three turned towards the door to see Krampus walk in, holding a bloody hook on his chain and a scar across his face. His breath was ragged and heavy, his fur and cloak stained with blood, and his claws were broken on some fingers.
"You are troublesome… But no more… Now… Krampus will feast on your flesh" At this, he started running forward. His footsteps pounded on the stone floors, while the Marauders stood still, aiming the tree tip. James steadied the tree, while Sirius held his wand at the ready, Peter behind him. Krampus raised his chain and roared out, and he came with three feet of them when-
"Now! Locomotor Mortis!" Sirius shouted, freezing Krampus' legs, causing his momentum to fling himself right in the path of the tree, impaling him in the heart. His breathing became slow and ragged, and his arms went limp at his sides.
"It's over, Krampus. Merry Christmas." James mocked at the monster, and pushed the tree in further. At that point, Krampus' body began to change color. It became crystal white, clear as paper, and as frigid as ice. It covered him entirely, leaving him just a frozen version of himself.
"Well, that worked out pretty-" Sirius began, only to be interrupted by Krampus' frozen body being shattered and spread across the room in the form of snow. Three inches of the white fluff covered the entire Great Hall, leaving the Marauders in the middle of a miniature winter wonderland.
"I hate snow." Sirius mumbled.
"Wait, wasn't there something else we needed to do?" Peter asked, only to be greeted with a moan of an animal.
"Oh, right. Moony is a werewolf right now." James remembered, and knocked Remus out with a blow to the head.
"Prongs!"
"Oh, he'll be fine."