As an additional cost to cast this spell, discard X cards.
Target player draws X cards. Channeled Force deals X damage to up to one target creature or planeswalker.
If one of Channeled Force’s two targets becomes illegal, the other is still affected as appropriate.
If you cast Channeled Force without paying its mana cost, you still choose a value for X and discard that many cards. This is because the spell doesn’t have {X} in its mana cost.