Disgaea: Hour of Darkness Tips

Easy Level-Ups
Strong Sword (Cosmic Blade, Diabolic Sword,etc)
Winged Slayer (sword special)
High enough demon rank at Dark Assembly
Stronger Enemies Bill(if needed)
Weaker Enemies Bill(if needed)
Cave of Ordeal Bill
Get to episode:Captain Gordon Defender of Earth.

Go to Stellar Graveyard and enter Valgipus IV. Then you'll see the enemies in a giant sqare. Use winged slayer on them and you'll gain like 3-10 levels and 11,000 hl. You can use the stronger enemies bill for more exp and hell.

Go to Cave of Ordeal and enter cave no.3. Use the same stratgy above.