Implacable.

[MaxAstro]

For reference, as my current game as the Grigori, I have 7 or 8 non-adventurer units at that level, most of which are mounted units. If I were the scions, they would be waging war right now.

 

[Vehem]

I think nothing finishes an army like a crack troop of Implacable Principes, but wouldn't mind waiting longer/working harder to get them.

If it's aimed at units around that level, it'd probably pay to TechPrereq it at a similar level, or slightly above to make it an "upgrade" tech for the unit. Or possibly make the TechPrereq Fanatacism so that it's available to other units at the same time that Revenants become available?

I think the main concern is that the early barbarian leveled units are finding it too easy to obtain (I haven't tried doing so with the Scions, but with most other civs I could easily gain enough XP to take Implacable on half a dozen or so units before I had more than 3 cities. If nothing else that makes them impossibly good defenders (2 units with bonus first strikes and very rapid heal rates in each city).

Having the TechPrereq set to Fanatacism would probably be just about the right time.

1-3 more levels required should put the kibosh on "stacks" of lower-tech units with it.

Levels can come very quickly or very slowly - it's hard to balance against them or to plan for them as a player (part of the problem with the Elohim monks). The tech however is a known target. Even if it did still allow numerous Scions units to become implacable, it has become an upgrade that you've worked toward and achieved rather than just a no-brainer choice of promotion.

 

[Tarquelne]

This is what I think I'll do:

Make the prereqs Fanaticism (by far the most fitting tech) and Combat V
Remove Mounted from the UNITCOMBATS.
Probably add a Redactor spell that gives a promo (not Implacable) to MOUNTED units. (Redactors can give the Gift to the horses.)
Perhaps reduce the Healing rate in enemy/neutral territory.

I'm not very concerned about Implacable's power, but I do want it to seem special. I think my superior different play-style kept purchases of Implacable sufficiently rare in my games, but that's not holding true for others.

 

[Valkrionn]

This is what I think I'll do:

Make the prereqs Fanaticism (by far the most fitting tech) and Combat V
Remove Mounted from the UNITCOMBATS.
Probably add a Redactor spell that gives a promo (not Implacable) to MOUNTED units. (Redactors can give the Gift to the horses.)
Perhaps reduce the Healing rate in enemy/neutral territory.

I'm not very concerned about Implacable's power, but I do want it to seem special. I think my superior different play-style kept purchases of Implacable sufficiently rare in my games, but that's not holding true for others.

Sounds about right, much as I'll miss it early-game. As for the mounted promo, how about something that gives heal rate, possibly even as much as Implacable, while reducing defense? Make them easier to kill, while at the same time allowing them to absorb more minor hits.