Summoning Process Details
When 2 are selected to summon a new Hero, each attribute of the Hero will be mixed between Hero A and Hero B:

Character

Character of Hero C = 50% Character of Hero A or 50% Character of Hero Bโ€‹

Class

Class of Hero C = 50% Class of Hero A or 50% Class of Hero B

Origin

Origin of Hero C = 50% Origin of Hero A or 50% Origin of Hero B

Attack Type

Attack Type of Hero C = 50% Attack Type of Hero A or 50% Attack Type of Hero B

Equipment

There are 3 equipment slots, with the similar behavior. Let's go with Equipment Slot 1.
Chosen Equipment = 50% ( one in the combination of Equipment 1 of Hero A and 3 Equipment of Hero B ) or 50% ( one in the combination of Equipment 1 of Hero B and 3 Equipment of Hero A )
After the Equipment is chosen, there will be 2 cases depending on the rank of Equipment:

Chosen Equipment is Rank 0

There are 2 more sub cases depending on the Percentage of Evolution:
Percentage of Evolution = ( The percentage of Evolution of Hero A * The percentage of Evolution of Hero B ) / 2

Evolution

Final Equipment 1 of Hero C = [ 33% (Equipment 1 of Hero A combine with Equipment 1 of Hero B) or 33% (Equipment 1 of Hero A combine with Equipment 2 of Hero B) or 33% (Equipment 1 of Hero A combine with Equipment 3 of Hero B) ]

No Evolution

Final Equipment 1 of Hero C = Chosen Equipment

Chosen Item is Rank 1

There are 2 more sub cases depending on the Percentage of Degradation:
Percentage of Degradation = ( The percentage of Degradation of Hero A * The percentage of Degradation of Hero B ) / 2

Degradation

Final Equipment 1 of Hero C = 50% ( Rank 0 of Equipment 1's component ) or 50% ( Rank 0 of Equipment 1's component )

No Degradation

Final Equipment 1 of Hero C = Chosen Equipment
The same applies to Equipment 2 of Hero C, Equipment 3 of Hero C

Runes

There are 3 rune slots, with the similar behavior. Let's go with Rune Slot 1 of Hero C.
Rune 1 of Hero C = 50% ( one in the combination of Rune 1 of Hero A and 3 Runes of Hero B ) or 50% ( one in the combination of Rune 1 of Hero B and 3 Runes of Hero A )
The same applies to Rune 2 of Hero C, Rune 3 of Hero C