When this card is Normal Summoned, it is changed to Defense Position. If you have no cards in your hand, this card gains the following effect: Once per turn, you can select 1 "Infernity" monster in your Graveyard, except "Infernity Necromancer", and Special Summon it.
Sangan is a great searcher in Infernity decks because of his fitting type and attribute. You can revive Infernity Beetle with Infernity Necromancer's effect and use both of them with Sangan to make Hundred Eyes Dragon.
Here are some of the monsters you can revive with Infernity Necromancer's effect.
You can swarm the field by revive Infernity Necromancer with Debris Dragon and then using Infernity Necromancer's effect to revive another monster. You can then use Debris Dragon and Infernity Necromancer to make a level-7 Synchro monster.