Obelisk the tormentor is only available as a download.
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No. Because Fiendish Chain targets a monster, Obelisk the Tormentor will not be affected by it.
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Yes. Because Obelisk the Tormentor is only protected from card effects that do not target, Tribe-Infecting Virus will be able to destroy Obelisk the Tormentor via its effect.
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Obelisk the Tormentor (Effect Monster) is not Ritual Summoned nor does it require a ritual. To summon Obelisk the Tormentor, you must Tribute 3 monsters (it is treated as a Tribute Summon).