To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions (such as that of Saheeli's second ability)
It also gets even better with Sazh's Chocobo and other +1/+1 counter cards
Honorable Mentions The One Ring, Teferi's Protection, Perch Protection, Noble Heritage, The Stasis Coffin, and Absolute Virtue are all cards capable of giving you protection from everything which still stops spells and abilities from targeting you
Outside a copy of Eldrazi Temple, this mana base is pretty bad, and it needs a lot of work and restructuring
Since we're milling so much the deck also has a reanimator subtheme
The one awkward part about this card is that usually low-to-the-ground decks with lots of creatures really want to be attacking, and Knight-Errant needs to be convoked to provide extra value