The Mother of Dragons is a building in Draconius Go where you can hatch Ancient Eggs. It can only be found inside the Rift of Arcana. However, not all rifts contain the Mother of Dragons.
Most of the time it can be seen immediately after using a portal to enter a rift if there is one present.
Mother of Dragons Usage
Once you have found the mother get within range and tap on it. This will show a menu where you can choose which Ancient Egg you want to incubate. You may now put an egg in one of her cocoons.
Normally you can only place one egg with the mother. You also cannot place eggs with multiple dragons. You must wait either 2, 5, or 10 hours depending on the egg that you selected before starting another egg. This limit can be raised by equipping various artifacts such as the Dragon’s Heart.
If the rift closes (the portal disappears) before your egg is hatched then it is returned to you and you will have to find another rift with another Mother of Dragons to continue the incubation.