This mod adds new tiers of Toxic biters which have the same progression as Category biters from Schall Endgame Evolution.
New Category Toxic Biters are displayed in Schall Endgame Evolution UI.
Mod settings from Schall Endgame Evolution will also be applied to Toxic biters.
To remove infected entities from Schall Endgame Evolution UI set "Exclude spawners" mod setting to new defaults.
Both Toxic biters and Schall Endgame Evolution mods are required.

This extends Schall Endgame Evolution support of Toxic Biters.
Leviathan Toxic Biters are removed.
Mother is reworked:
1) Added a new weaker mother with 6000HP which appears with behemoth enemies at 0.9 evolution and can spawn big biters and spitters.
2) Old Mother is renamed to Big Mother, has 48000HP by default and spawn behemoth biters and spitters.
3) Big Mother strength can be changed in the settings.
4) First appearance of Big Mother will depend on Schall Endgame Evolution difficulty. By default, it appears at 0.99 evolution at difficulty 1. The stronger the mother, the later it will appear.
5) Big Mother can be disabled in the settings.
6) The birth rate of Mother and Big Mother can be changed in the settings. By default, they will spawn 1 biter and 1 spitter every 10 seconds while engaged in combat.

If you want add Mother and Big Mother to normal biters try mod Mother

When playing with Milestones there are new milestones with category toxic biters.
For existing saves, you should click Reset in Milestones UI to bring new milestones.

There is also an optional balance change named "Fair pollution cost" which is disabled by default.
It makes category toxic biters and spitters pollution to join attack values scale with their strength in more linear way.
This may be considered as Difficulty 0 pollution price setting which is more fair to player.
For example, pollution values to join attack for Category X toxic biter with 192000HP:
Difficulty 9: 400 pollution (Same as behemoth biter)
Difficulty 1: 2800 pollution
Fair pollution cost enabled: 13605 pollution

To apply "Fair pollution cost" to normal category biters use Schall Endgame Evolution Tweaks mod.
This mod also recolors category biters to add a bit of diversity to the game.

Also check out another biter mods with Schall Endgame Evolution compatibility:
Armoured Biters
Explosive Biters
Frost Biters
Acid Biters

If you play with Krastorio 2 you may also use Toxic Biters K2 Compatibility mod.