.Techniques.
Orochimaru has quite a few tricks up his sleeve; top level ninjutsu along with his own developments and forbidden techniques. Unfortunately I can't catch all the Japanese names, but I'll try and search.

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Gogyo Fuuin (Five Element Seal)
-He used this to forbid Naruto from using the Kyuubi's chakra.

Kuchiyose no Jutsu (Summoning Technique)
-Like the other Sannin, Orochimaru summons an animal clan to battle. His animal is naturally the snake.

Juin Jutsu (Curse Seal)
-By biting someone with those fangs of his, Orochimaru gives his prey the cursed seal. It causes horrible pain and there's only a 10% chance of survival. If you survive, you'll have a strange new type of chakra at your disposal.

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Furou Fushi no Jutsu (Immortality Technique)
-This technique keeps Orochimaru alive and stops him from aging. His soul is attached to this world, all he needs to do is now and then find a new body where to keep his soul in.

Edo Tensei (Reincarnation to the Impure World)
-This is a powerful and forbidden technique Orochimaru uses while fighting the Third. The user is able to revive anyone by binding the dead to the living world through live human sacrifices.