IMO whatever your endgame build is, it'll generally be good enough to make the ascent. A few things to consider:

• Health pots: Mobs in the Demon Halls and lower Metropolis levels can be aggressive.
• Food: Make sure you have enough food. If you're still trying to grind XP to make Level 30 you'll need enough not to starve in the mid levels. This shops would probably have rations, but those are thin gruel in needy times.
• Scrolls of Transportation and Stones of Blink can get you out of trouble of you get cornered by aggressive mobs. Same for Scrolls of Terror and Stones of Fear
• Potion of Mind Vision + Psionic Blast are good for clearing levels out of you want to hustle through, but mind the Amulet getting too strong
• Invisibility helps, but eventually the Amulet gets too powerful, and you'll run out of invisibility options

Once I make it back up to the Mines, I find the rest of the ascent to be pretty easy. It'd be pretty cool if the Rat King reacted to the Amulet somehow and stymies your ascent undltil.you defeat him. Maybe you couldn't kill him, but it would be fun to have to knock him down below 25% to get past him, like the crystal guardians in the Mines quest-- a sort of bonus final boss near the and of the game? Maybe make it harder if you didn't present him with the crown first. i see why not, though.

I digress... Hope the tips are helpful! I don't find the Ascent to be too difficult, myself.

You get full health and hunger after each chapter on the way back up. Shouldn't need any health pots. Also generally at that point in the game you're already OP lol.