Rulings

Threads of Disloyalty can't target a creature with mana value 3 or greater. If it somehow enchants a creature with mana value 3 or greater, Threads of Disloyalty is put into the graveyard the next time state-based actions are checked.
Creatures on the battlefield treat {X} in their mana cost as 0 for the purposes of calculating mana values.
Tokens usually have a mana value of 0.