Do you mean Aqir?

yes

A good start:

https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2997442612

"Aqir Seed Units
When a seed unit dies, it will spawn a unit based on the hero level of the unit that didn’t die
For example, we play a typical 2 aqir / 4 beast build

Look at the following typical Arc Aqirs set up from a Serbian Butcher game:



He is playing 4 beasts and 2 aqirs with 2 Lone Druids, so when the first Lone Druid dies, he will spawn an aqir unit based on the surviving heroes level (in this example, they are both level 6 units).

A level 6 unit would be a 2* Brood or Nyx (as that is the same level as the remaning unit). If one of the Lone Druids had Witless Shako and the other unit died, the spawn would be a level 7 spawn - a 3* Veno or Sand King

This can make a huge difference in the fights. And is especially useful on 2* Legendary units if you have a 1* seed. This then allows you to spawn 3* Brood and 3* Nyx assassin which are no joke!

Here is the link for the Arc Aqirs game btw in case you're interested in watching - Serbian Butcher is famous for his aqirs, so if you are interested in learning, I highly recommend watching his videos!"