Relics info?

It's difficult to answer exactly how much stats increase, since different characters have different stats that are increased. Strength based heroes gain a higher modifier to increases in strength, for example.

Also you need relic to boost your "mastery", which only unlocks at relic level. Mastery is a stat that boosts various other stats, based on the type of character and what they are good at. Attackers typically gain damage, accuracy, crit damage etc., while tanks gain armor, health, protection etc.