I had an idea for this, and I hope it goes as well as I'm picturing it.
For convenience's sake, everyone except those who can't talk speak the same language. Sorry if it bugs some people.
Hiccup glared down at the clouds. They were so thick, he couldn't see below him.
"C'mon, bud. Let's go lower."
Toothless let out an uneasy growl and swooped lower.
Hiccup stared at the unfamiliar landscape. Where were they? It wasn't a small island. Probably much larger. A continent. Where had that storm taken them?
Toothless suddenly dipped left. Hiccup took one look at the fin and realized why. They were falling. He stared around in a panic as the ground came up, and fast.
Hiccup tried to pull Toothless upwards, and the landing was rough. Hiccup was thrown from the saddle, and everything went dark.
Hiccup forced himself to his feet and stared around. Except for a throbbing headache and a couple scratches, he wasn't too badly hurt. He began to quickly realize someone was missing. No Night Fury in sight. He looked wildly around. Where could he have gone? Did someone grab him? Did he wander off? Hiccup saw Toothless's footprints headed in a direction. He followed them with his eyes. His eyes rested on a mountain peaking above the trees.
"Where are you going, bud?"
Picking up Inferno, which had been dislodged in the crash, he began to follow his dragon.
Hiccup finally made it to the base of the mountain. Toothless's tracks were nowhere to be seen, but they hadn't changed course once. He stared up at the huge rock.
He began the long trek up, working his way up the rocks and grumbling under his breath about Toothless deciding to abandon him. That fact worried him. He finally made it to the top. Staring around, he managed to see nothing but forest.
He looked behind him and saw what looked like a cave. He walked forward, and suddenly, he felt his peg leg get caught on something. Before he knew it, he was falling into a huge hole. He couldn't see the bottom. And after what seemed like forever, once again, he hit something, probably the ground, hard. Everything went black again.
Hiccup's eyes fluttered open, and he looked around. He was lying in a bed of yellow flowers. Something about it comforted him, and since his entire body was too sore to move anyway, he relaxed himself for a long time in them. 'Toothless.' He began to struggle to his feet at that. Managing to stand, he began to pick his way through the only tunnel out. 'Or at least, I hope it leads out.' If not, he was trapped down here. There was no way he could climb back up through that hole he had fallen down.
He looked up at an archway he hadn't noticed until he was practically under it. 'An arch? Down here!?' Pushing it down, he noticed a symbol on the top. A winged circle over three triangles. 'What the..?' Deciding to ignore it, he pressed forward. Hiccup saw a small hill, and on the other side of the room, another identical archway.
He continued, almost walking past a single flower sticking out of the mound. He looked at it, raising an eyebrow. It was much larger than the others. He moved up to it, and much to his surprise, it MOVED to look at him. Yes LOOK, it had a face. Hiccup let out a surprised yelp and fell backwards, backing up. The flower stared at him with a big grin.
"AHHH!" Hiccup backed up more. "Keep away!"
The flower looked hurt. "Hey, pal, it's okay! I'm your best friend! "
Hiccup stared, shocked.
"Golly, you're new down here, arent'cha? Well, your old pal Flowey will help you out. This is the underground. Down here, we get stronger using LV! I'm sure you have a weak soul. All you need is a little of that LV!"
Hiccup got himself into a kneeling position. "Let me get this straight. You're a talking flower, and this is an underground area. Okay. How do I get out of here, and did you see a big black dragon?"
Flowey stared at him for a long moment. "Okay.. pal. I don't know about any black dragon, but why don't you look for him after I help ya out? You won't last very long down here without LV."
The flower sighed as if it was talking to a child. "Love, du.. silly!" It grinned some more.
Hiccup stood up. "No thanks. I'll be fine."
Flowey's voice became lower. "Oh, but I insist."
Hiccup was surprised to see a bunch of little white.. things appear out of nowhere. They twirled, and looked harmless enough.
Flowey stared at Hiccup. "Have some friendliness pellets, pal."
The white pellets flew forward on cue, all headed for Hiccup. He found himself dodging them.
"Hey!" Flowey looked upset. "You're supposed to run into the pellets!"
Hiccup began to back away, not sure he could trust this thing. Before he could blink, he was surrounded by "friendliness pellets". He gasped as they closed in from all sides. Flowey apparently found it amusing, because he was laughing, and had a twisted, creepy smile.
Hiccup ducked through the biggest gap he saw, wincing as some grazed him. He was only half shocked to see they hurt him, even drawing blood. He turned and ran through the other arch, inwardly bidding his "best friend" goodbye.
He hoped he never had to see that terrible thing again.
Yup. A crossover. If you didn't bother to read ths story description.
Did you notice the italicized words? Two of the tracks from UT. Quite a few will be in here.