Typucm
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Regarding the specialty, as I understand it, everything is quite simple:
For each level that is a multiple of the creature's level, the hero receives a bonus:
(1 + hero_level / creature_level) * 5%
to the attack and defense of these creatures. Round up.
Of course, this does not apply to Conflux heroes, campaign heroes, and others that provide a fixed bonus to creatures, regardless of level. For example, there are two Black Knight specialties - one depends on the level, the other does not.
Adel has almost the same thing, only instead of attack/defense, the blessing bonus (unit) given to that level of creatures increases.