The Immortal Sun
Legendary Artifact
Players can't activate planeswalkers' loyalty abilities.
At the beginning of your draw step, draw an additional card.
Spells you cast cost 
less to cast.
Creatures you control get +1/+1.
Kieran Yanner
Commander Masters (CMM)
• #393Rulings
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. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.
(wotc • 2018-01-19)
Rulings
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. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.
(wotc • 2018-01-19)