yeah it hidden you need to active abyssmystery for gain intoabyss active it when turn has pass after active intoabyss for 4 turn you will gain Ancient ritual art for innate skill and and you need to use it on abyss summoner sacrifice it to gain call mother it mean you need to unlock source 3 to combo for call of mother. abyssmystery and intoabyss is main key for get all abyssal skill works full potential.

OHH, I understand now, Thank you for the help understanding that. Is there a reason we need three source for the combo? does the Kraken have over-the-top and overpowered skills for a summon?

up to you kraken summon by abyss summon is 1 but mother can summon 2 kraken

maybe there is a mod incompat with my setup then to summon the abyss summoner i need 3 source points

https://ibb.co/rZmxBh2

yes it 3 source skill