[ Machine / Effect ]Cannot be Normal Summoned/Set.
Must be Special Summoned with the effect of a "Drytron" card.
You can Tribute 1 other "Drytron" monster, or 1 Ritual Monster, from your hand or field; Special Summon this card from your hand or GY in Defense Position, then you can add 1 Ritual Monster from your Deck to your hand.
You cannot Special Summon monsters, except monsters that cannot be Normal Summoned/Set, the turn you activate this effect.
You can only use this effect of "Drytron Alpha Thuban" once per turn.
ATK/ 2000
DEF/ 0