Soul Stones/Titan

Titan Soul Stones are used to evolve Titans. They can be obtained in the Circle of Summoning or through Special Events.

Summoning Titans (with soul Stones)
most titans are summoned at 1 star (for 30 soul stones), but Super Titans are summoned at 3 stars (280 soul stones)

considering that Super Titan Soul stones are rarer to come by; only coming from Chests of Super Titan, Events, and duplicate unlock of that titan: it should be far more likely to summon a Super Titan from unlock (otherwise 250 soul stones saving 30)