Introduction
In Sacred exist 11th secret dragon. It was accidentally found by russian player WORTLOS in august 2016 (and only in 2018 was published ru-guide about it, after my returning to managing ru-community).
Thats a secret dragon (or baby dragon). For his appearing you need about 3 hours of real time.
How you can get it
You need "Helkemel, Traveling Merchant". You can find him near to bridge on the road to Mystadale.
Helkemel offers to buy a dragon egg, But you need to choose "Reject".
After that move away for a some range. Check mini-map, when Helkemel's dot turn from white into gray (it means he dead) you can return.
Speak with dying Helkemel. He tells that dragon has hatched and need to catch it before he grows...
You can find hatched dragon at east from the Mystdale, below graveyard...
...and it's just a raptor.
BUT, after 7 ingame days (about 3 hours in real time) baby-raptor will become a big dragon!
It's stats should be same as Draconis Mortis, cause it's same dragon type.
Conclusion
As I know, it's the last detected secret in Sacred and no one knew that baby dragon can grow up. All hints about it was in sight, but a long time required for baby dragon growing hide it from players for more than 10 years.