Whenever you cast a spell, if its mana value is equal to 1 plus the number of soul counters on Obscura Ascendancy, put a soul counter on Obscura Ascendancy, then create a 2/2 white Spirit creature token with
flying (This creature can't be blocked except by creatures with flying or reach.).
As long as there are five or more soul counters on Obscura Ascendancy, Spirits you control get +3/+3.