The other Darkin

I was going around the wiki and other boards post looking up info on the darkin because my friend told me there have been mentions of a 4th and 5th darkin in lore somewhere, and i think that would be so cool if we could have a full darkin team.

Aatrox is a top laner Kayn/Rhaast is a jungler Varus is an adc

and so the last two could be the remaining roles! maybe the confirmed by Varus girl darkin could be the midlaner and the remaining one could be a support?