Cryptic Serpent
Creature — Serpent
This spell costs 
less to cast for each instant and sorcery card in your graveyard.
It slithers through the senses, constricting consciousness and poisoning perceptions.
Lius Lasahido
Commander Masters (CMM)
• #83Rulings
A split card only counts once for Cryptic Serpent's ability, even if it's both an instant and a sorcery.
(wotc • 2017-04-18)
Cryptic Serpent's ability doesn't change its mana cost or mana value. It just reduces the cost to cast the spell.
(wotc • 2017-04-18)
Cryptic Serpent's ability can't reduce its cost to less than {U}{U}.
(wotc • 2017-04-18)
Rulings
A split card only counts once for Cryptic Serpent's ability, even if it's both an instant and a sorcery.
(wotc • 2017-04-18)
Cryptic Serpent's ability doesn't change its mana cost or mana value. It just reduces the cost to cast the spell.
(wotc • 2017-04-18)
Cryptic Serpent's ability can't reduce its cost to less than {U}{U}.
(wotc • 2017-04-18)