Monsters

Raviel, Lord of Phantasms
Beiige, Vanguard of Dark World
Sillva, Warlord of Dark World
Goldd, Wu-Lord of Dark World
Phantom Skyblaster
Grinder Golem
Grave Squirmer
Sangan
Metabo Globster
Caius the Shadow Monarch
Kuriboh
Doomcaliber Knight
Gorz the Emissary of Darkness
Doom Shaman
Giant Orc
Morphing Jar
Dark Ruler Ha Des
Skyblaster Token
Giant Germ (easy summoning of 2 Fiend's)
Tragoedia (quick summon, like Gorz the Emissary of Darkness)
Renge, Gatekeeper of Dark World (Good Defense)
Emperor Sem (Good Defense and with all the sacrifices for Doom Shaman, Caius the Shadow Monarch, and Dark Ruler Ha Des, it makes for excellent returns
Puppet Master (good for summoning raviel with its effect)
Wall of Illusion (good defense)
Slate Warrior (good offense)

Spells

Card Destruction
Dark World Lightning
Gateway to Dark World
Dark World Dealings
Multiply
Detonate
Fires of Doomsday


Traps
Ojama Trio
The Forces of Darkness
Dark Deal
Light of Intervention
Swords of Revealing Light

try including some tuners such as Fiend Roar Deity Raven, for synchros, they might come in handy you know, and another card recommended for such deck is Darkness Neosphere (4000 atk and def, really too easy to summon, and on top of that, can't be destroyed by battle!completely no flaws!) and maybe an Infernal Gainer can be useful too.Ha Des is not that much of a card.and don't rely any more on Multiply/Kuriboh combo,just think about it, the chances of drawing those two cards together are too slim.
hope i helped; good luck, and stay active!

lol sorry the completely no flaws part about Darkness Neosphere made me laugh, so many decks have multiple ways of destroying cards other than battle.

meh its hard to tell exactly whats in your deck, you posted Giant Germ but then next to it you have 2 easy summons so not sure if you only have 1 in deck or 3. Try to make your post of deck list more clear