I would like to report either an issue or a bug in the mod.
I currently am playing Divine Rpg and I am having too many Whales Spawn that it literally makes the game unplayable.
I have tried SpawnTableTweaker and InControl to try and fix these spawn rates of these guys but to no avail. There is over 100 to 200 that spawn in one area and in caves with 1 block water sources that it literally makes my game unplayable.

Here is two pictures I managed to capture showing it after waiting like 2 minutes for the game to catch up from the whale spawns:

Not able to modify 1.12.2 is different of not wanting. The code is still there on github, it just finding the cause, fix it and make a new version!

The solution you are proposting its idiotic to be simpatic!
Or you have this commands running every 2 seconds since its what it takes to spawn 2 thousand wales and constantly degrading the server or play in peaceful and have zero mobs in the game......

Even if I wanted to I couldn't. Forge is no longer supporting 1.12.2 dev environments. Ive simply provided a work around and not a fix. There is nothing more i can/will do to fix this.

Same with Rainbour ahhh >.< I'll just use the 1.16 version

Since we are unable to modify 1.12.2 source anymore i am forced to close this issue.
However
A temporary fix is

/kill @e[type=divinerpg:whale]
/kill @e[type=divinerpg:shark]
/kill @e[type=divinerpg:liopleurodon]

However this isnt an ideal end solution

An alternative solution switch to peaceful then switch back