Ascending Heroes increases the stats of those heroes. An improved stat growth - Strength, Intellect, and Agility - will be applied to the hero and take into consideration the number of levels your Hero already has. That means it does not matter if you ascend your Hecate to five stars at level 60 and your friend ascends their Hecate to five stars at level 20. When both Hecates are same level, they will have the same stats. Five stars is the max level of ascension.
For each ascension, bonus stats other than that from stats growth and level is added. The bonus stats is 2*(ascension stage) each for STR, INT and AGI. i.e. From one star to two star, it is ascension stage one, it gives 2 STR, 2 INT and 2 AGI. From two star to three star, it is ascension stage two, it gives 4 STR, 4 INT and 4 AGI. Altogether from one star to three star, it gives 6 STR, 6 INT and 6 AGI.
|★ → ★★||20||35,000|
|★★ → ★★★||50||120,000|
|★★★ → ★★★★||100||300,000|
|★★★★ → ★★★★★||150||800,000|