The card that makes the deck as strong as it is; an instant search every time you special summon it.
The most obvious use is to special summon it, then use it as synchro or xyz material so that you can put it into the graveyard to be summoned again.
Strategies and game play:
The strategy of most Infernity decks is to repeatedly special summon this card to take full advantage of the pluses it generates
Combos with other cards:
First, anything that lets you special summon it: Infernity Launcher, Infernity Necromancer, Infernity Mirage, etc.
Keep in mind that it can search ANY Infernity card, including the spell/trap cards.
Dark Grepher, Armageddon Knight, or Foolish Burial can be used to put it into the graveyard, which is the easiest place for Infernities to summon it from.
Lavalval Chain, A Feather of the Phoenix, or Plaguespreader Zombie can be used to place it onto the top of the deck, where it'll special summon itself as soon as you draw it.
Ways to counteract it:
Thunder King Rai-Oh can run it over and keep it from searching another Infernity card, stopping the whole deck dead in its tracks.
Macro Cosmos and, to a lesser degree, Dimensional Fissure (which can be worked around by Xyz summoning) can be used to keep it out of the graveyard, where it can't be repeatedly spammed.
First, it's triggered by special summon and is easily spammable. This means that one can easily get 4 or more searches from it in one turn.
Second, 1800 ATK is pretty good.
In general the "magic number" for level 4 monsters is 1900, and Archfiend doesn't quite get there.
Originally printed in English as a promotional card for the DWC 2009 DS game, it was later reprinted is Gold series 3. I know there's a Japanese version, but I don't know what set it was in.
Artwork and aesthetics:
It looks pretty bad***.
Broken card is broken, "not as broken because counterable" argument is stupid. Yet it is also balanced by its relatively low attack that's still not bad.