Mod requests (orders).

Something like that, but I might be wrong.

To make Twilight Witches recruitable in the building for hiring Hydras.
In the file
\GameMechanics\TownBuildingSharedStats\Dungeon\Dwe lling_5\DampCavern.xdb
In the line

CREATURE_HYDRA

Change the ID CREATURE_HYDRA to CREATURE_MATRON
My ID reference: All_ID_Heroes_V.doc

To make Shadow Mistresses and Night Hags recruitable in the building for hiring Cave Hydras and Dark Hydras.
In the file
\GameMechanics\TownBuildingSharedStats\Dungeon\Dwe lling_5\ChaosCavern.xdb
In the lines

CREATURE_CHAOS_HYDRA/Creature>
CREATURE_ACIDIC_HYDRA/Creature2>

change the IDs to CREATURE_MATRIARCH and CREATURE_SHADOW_MISTRESS

To make Hydras recruitable in the building for hiring Twilight Witches.
In
\GameMechanics\TownBuildingSharedStats\Dungeon\Dwe lling_6\MatronChambers.xdb
change the ID
And in
\GameMechanics\TownBuildingSharedStats\Dungeon\Dwe lling_6\MatriarchChambers.xdb
change the ID as well.

Everything else is cosmetic customization; it's not difficult.