CaptAhab's Guide to FHP

I (Zebulon) made some edits to improve readability, but this is the guide as I received it.
===The Guide===
Go invis and stay invis throughout the cave. If you have the spell Greater Invis use it every couple of fights, if you are using potions, have plenty, you do not want to become visible in a room full of devils. I would invull too just in case. The general strategy, most know this and hey it works, is to become invis before the fight, and use summons, FQ's and/or Demons as bait. Then use a mass room damage spell of your preference to beat the critters down. Multi Blade/WoG/EF etc. 
Note: Anywhere I call for a Demon and you do not have that spell, FQ's will work, it will probably take several though, so keep em flying.
Enter cave. Ignore wraith guy, enter sarc, ignore bats, go Up 1, L 1, Up 1, kill Dark Faerys (have to kill them to move through.) Go 1 Up, 1 L, kill undead, they will sometimes drop semi rare spellbooks so look for that.
Go L 2, kill Furies, I use a couple of demons here they last longer than FQ's, then mass room damage spells, and maybe the thrower for any late almost dead stragglers. Now Down 1, through door, Down 2, kill Lichs. (Again at least a couple of demons and room damage spell of choice.) Go 1 R, check sarc.
Now backtrack the way you came. 1 L, 4 Up, 1 R, 1 Up, 1 R, ignore rat and sarc (it is empty.) Down 1, R 4, kill Troll Kings. 
Know that they EQ a lot which can fumble your weapon, make sure it is still equipped if you decide to attack in later rounds. 
Up 1, L 1, ignore any critter that may be here, check bone pile (hey you never know) R 1, enter door in floor. Ignore Cyclops. L 1, kill Imps. Backtrack 1R and 1 Up.
Note you are not in the same room you were in before. This door is in the middle of the room. But that's alright, we have dodged some switch throwing. 
Go R 1, and Down 1, kill Bounty Hunters. 1 Demon works well here. Go back the way you came, Up 1, L 1. 
Now there is a devil 1 D and some bats after the devil, not worth the trouble IMO. Enter door. (or come back and enter after you killed the devil/bats) Make sure you have fresh invull and invis then go D 1. Kill devils. FQ's work better here than demons, the devils can beat a demon down pretty quick and have to chase FQ's. Get 3-4 FQ's up then room damage away. Throw the switch when you have handled the devil problem.
R 1, ignore Cyclops. R 1 more, kill devils just like you did the last time. Check bone pile. L 1.  Now these two doors are optional if you are only looking for levels. Not much xp to gain in either direction. If loot is a concern, and as of this writing loot pretty much sucks here, but if you really want to... 
Take stairs, ignore 2 Thieves, then Down 2. Check bonepile. Kill ghost or not... Go back the way you came till you see the Cyclops, wave at him for me, then enter door. Up 1, kill Thieves, R 1, check loot. Backtrack to our old buddy the Cyclops, Go L 1, Up 1, ignore Cyclops #2. 
Hit the switch in lower left corner. Go R 1, kill Cyclops group. Throw switch. Back in the switch room there are 2 switches on right of screen. Throw the top one.
Down 1, now L 1 are some Bounty Hunters, up to you, I pass on em. From here Down 1, L 1, Down 1, kill Medusas. A couple of FQ's work well here. L 1, kill Devil/Warrior combo. Last loot check is Up 1. Then Down 1. Throw switch. Activate the 2 buttons in floor, then throw the switch just to the right of the Cyclops. 
You are back at the cave entrance. Go out, come back in, and do it again. This guide gets you all the big xp fights, checks loot locations, and getsyou back to the entrance. Level on Realmers :)