The only core factor here is Monster Strength. Other settings will largely affect how long you want to suffer under these conditions. All routes eventually lead to rolling through the game with stupidly strong characters.

That said, the most impactful will be EXP multiplier. Since everything in the game will instantly end your run, you're only going to get a single opportunity to get a little bit of EXP per fight in the beginning. However, this can rapidly snowball to you being able to level insanely quick once you're able to survive as your characters will be able to level attack skills much faster than with lower monster strengths.

Something to note is the game is not balanced around 10x Monster Strength. The developer has stated things about potentially adding systems in the future to better help overcome specific stat walls but until we have access to such systems, this guide will simply go through what's available in the Prelude exclusively.

Throughout your run, success is going to come down to how effectively you can reduce incoming damage. You can't do anything to fight back if you get rolled at the start of every encounter.

Agility is an option, but the later bosses and enemies will be too accurate to rely on this and it gets outscaled very quickly. For example, the second major boss has an accuracy value of 2600. That's roughly 1300 levels of dodging.

On that note, skills stop providing stat bonuses after level 999.

Aside from not getting hit, armor and block are your most direct way to reduce damage. Armor suffers from the same problem, with it being too low once the enemies ramp up. Something to note about armor however:
Having less than half the defense against the attack will increase the damage you take.
Having more than twice the defense of the attack only blocks 75% of the damage.
This means for the enemies dealing thousands of damage in a single hit, defense alone won't be enough.

Shield and Lanterns are great for blocking attacks early in the game. In the final release, you will also have a perk that will allow you to block without them. Keep in mind, you still take 25% of incoming damage when you block. However, this applies in addition to other modifiers such as defense and debuffs on the target.

Weak is critical as a status effect for surviving. Accessed through Green Magic or Axe skills, this can reduce an enemy's damage by up to 80% in addition to all other reductions.

Progression is simple. Set up your starter buildings and dive in.

[Leveling]
Race/skills do not matter. If you want to level up something specific, just equip it. Pray you live long enough to use any ability before you die. Any ambush is an instant wipe.
Getting killed still counts as being hit for the sake of leveling armor skills.

[Recommended Gear]
Large Shields are best if you want to maximum the time your characters have in a fight. Most if not all attacks until the boss are physical.
Small shield also works but has a low block chance.

Daggers and Fists with their fast attack speeds can level faster than other weapons.

[Cheese]
Imp's Signature ability can inflict poison. This will kill a hedgehog if successful.

[Upgrades]
Guild House upgrade is mandatory as you'll want to have access to the skill change system as soon as possible to level the skills you need.

[Goal]
Defeat the first boss and clear the dungeon.

Well done. You suffered long enough to kill the boss.

Now, we do the same thing with the 4-headed worm. The best part is you can use 8 party members.
Believe it or not, it gets faster from here. It's far quicker to unlock the speed bonuses which make attempts go by much faster. This naturally increases how much EXP you get over time.

[Recommended Gear]
If you have unlocked the Steal ability for any dagger user, equip it as it will give you some much needed loot.

The boss uses a mix of magic and physical attacks. You can stick with shields as your best bet since its magic attack has a longer cast time. You're still going to get rolled for the better part of the next couple of hours depending on your settings.

During this fight, you can have up to 10 pots. Use theft or loot to get as many as you can. Prioritize potions which grant status effects like Haste, Double, and Cascade which will increase how many actions you can take during the fight - as well as potions which recharge when you crit, block, or take damage.

[Upgrades]
You can detour to the next dungeon to collect the iron necessary to upgrade your storehouse and unlock item use. You can also upgrade the Guild to unlock additional bonuses.

[Goal]
Grind here until fighting it becomes trivial. Then reduce the amount of people being brought in to clear the fight. Your goal is to get 3 characters all powered up and ready to delve into the next dungeon.

If your 3 goons are at the point where they can easily shred the four-headed worm, you've officially hit the final breakpoint before the final boss of the demo.

[Upgrades]
You now hav the ability to collect iron ore. Use it to upgrade your Storehouse so you can equip potions and tools. Some of the rarer potions grant additional buffs when used which are sometimes way more potent than what you can cast (likely a bug).

[Recommended Gear/Skills]
Magic will be more of an issue from this point forward, especially during the final fight. Lanterns will help.
Attacks which apply shed or poison will bypass barrier. As such, Purrkin using fists, Red Magic, Axes, etc are great until you're strong enough to get through the barriers.

The final boss has high control resistance, as such is it recommended to avoid Slow and Dizzy abilities. Focus on applying Weak as quickly as possible to prolong the fight.

The final boss has around a whopping 200,000 total health as of v0.9.7. Have fun!