Module Upscalling

Hey folks, 

This isn't exactly a rush or anything, I got time. Since my players have been enjoying their first D&D experience, and Phandelver and Below ends at level 12 I was, I was thinking of moving. them to Icewind Dale when the current module is done. I actually was running them through Lost Mines initially, before I knew that basically got reprinted and expanded, but at the time I was considering moving the party north after the mines. 

Now I'm picturing, once the Shatterd Obelisk is done with, I'll use some of their factions to move em north, but have Icewind Dale start at level 12, and go up to 20. I don't know if this is common or not. I am aware that means I will have to go custom update every single stat block, but I'm curious if this even makes any sense to anyone. I was already planning on giving them a fright with the mind flayer colony up north, but have it wrecked by a sapphire dragon, do a bit of that back and forth since at this point they will be familiar with mind flayers. 

Likewise, I've already hinted at the mines having records of chardalyn, which I'm picturing being refined netherese, a material they are actively learning about in the current module.

I guess my question is: does anyone have a chart of what's roughly expected of a challenge for specific levels. For example, they might encounter the dragon at level 17 instead of 10 (idk, speaking hypothetically). Part of this would allow me to look for comparable CR creatures to tweak encounters they would RAW be overleveled for, but make it an appropriate challenge.

The big problem with major upscaling to a module isn't with upscaling combat encounters (that's just a numbers game), it's that a lot of the more mundane challenges just don't make sense upscaled -- 12th level PCs who do remotely reasonably preparation are just not going to have trouble with arctic weather, for example.

My optic was to bring them to Ten Towns and tackle that section as another investigative segment, trying to figure out what's going on. Something like Harper contacts going missing and rumors of a persistently long winter. Selling Icewind Dale that area not just everyone just wanders in, while also allowing them to keep the PCs they've grown to love for as long as possible. From there, the dungeon crawls will still make sense, and fighting zombie werewolves, an artificially created mecha dragon, and a literal god should still rile their adventuring bone. Though as you've said, that would require a complete numbers overall.

Quote from Acatia >>

My optic was to bring them to Ten Towns and tackle that section as another investigative segment, trying to figure out what's going on. Something like Harper contacts going missing and rumors of a persistently long winter. Selling Icewind Dale that area not just everyone just wanders in, while also allowing them to keep the PCs they've grown to love for as long as possible. From there, the dungeon crawls will still make sense, and fighting zombie werewolves, an artificially created mecha dragon, and a literal god should still rile their adventuring bone. Though as you've said, that would require a complete numbers overall.

 It's not just number, it's things like being able to teleport around to various different locations at the blink of an eye, or being able to create demiplanes and temples/mansions whenever they need them, or being able to Scry on the baddies whenever they want, or transform the entire party into eagles to fly into the BBEGs lair. 

Quote from Agilemind >> It's not just number, it's things like being able to teleport around to various different locations at the blink of an eye, or being able to create demiplanes and temples/mansions whenever they need them, or being able to Scry on the baddies whenever they want, or transform the entire party into eagles to fly into the BBEGs lair. 

Well to be fair, some of those issues are kind of easy to solve. 
Install some Hogwart-style no teleportation sigil in very important locations, just let them camp in their magic mansion, give the NPCs you want to keep hidden Nondetection or something like that, remind them that the book specifically mentions flying in a blizzard is a bad idea.

But I get what you mean, it will require some forethought. Then again, that's kind of DMing in general.

I don't have advice on upscaling the module, as this isn't something I've really done, but seeing as you are hooking in Chardalyn, they have released, in the Adventures in Faerun book, a monster called Zlan who is the forms of the seven liches merged into one who created the Crystal Shard. It controls others through Chardalyn and comes back after being slain six times a year, with a different lich taking control each time it dies. When you kill it for the seventh time in a year, it truly perishes. It's a pretty cool BBEG that leads to interesting exploration and mystery uncovering scenarios, and leans into the eldritch horror aspect of Icewind Dale. Zlan is melting Icewind Dale as his evil villain thing, and opening up steam vents and access to the Underdark, releasing monsters from below ground onto the surface. It is important to note that Zlan comes after the event of Frostmaiden, with references to the Chardalyn Dragon, but that can be easily enough remedied if you want to work both things in.

Huh! That could be an interesting follow-up. A multi-lich amalgamation does sound impactful. 
Would be a WHILE away from now, but still, having additional follow-ups might be what I need. I wonder if there's one for after Phandelver and Below since that's what I'm currently running.