Basically the Items you need are
500k Gold cash (100k for info, 400k for making the blade)
5 BIO Purity 11+ (25k a piece from TM)
1 Plat ore purity 10+ (25k a piece from TM)
Fate Book (dropped by Ghouls on Praj Island) - I got mine from 2nd ghoul I killed, but its random
GreyApeBlood (Find Grey Apes on 3rd floor or lower in Red valley) - Took me about 9 apes (this was with superspider bats too!)
The Cave
you need to clear all mobs (I tried killing just the generals - this didn't work)
I was an Assassin (Level 35) my gear was:
Fox Helmet, Medium Armour, Double Blades (Lk+1), 2x Death G, 2x Drag Ring, Black Boots / Lion Belt, AC Stone (M) and Quest Neckie
I tried a few times and I was always just out of time with a few mobs to spare,
I bought 3 Impact drugs from the GS (as advised) potted up and diced the cave with still over a min on my 3rd drug left.
Strategy:
I created 'zones' and worked from zone to zone
Before Fence - Cleared
Go Right and work Round - Cleared
Finish off clearing the mobs around the chest.
Try not to chase Archers for too long, wait for them to close in on you while clearing melee monsters, and then just flash dash them, so they wont run back and kill them.