Tervenna
Tervenna is the temperament tempering out 19683/16384, the Pythagorean augmented second, or in other words, it equates an octave-reduced stack of nine perfect fifths to the unison. This produces very flat fifths, as in 9edo – they are 666.7 cents, or in other words, flattened by 1/9 of the "comma". This is the tuning of 9edo, though like the compton family, the tuning of the primes larger than 3 is very flexible. 9edo is the unique tervenna tuning in the 5-limit that is also a mavila tuning.
Tervenna is part of the comptonesque series of temperaments, including itself, compton, and ntiscifer, which all temper different powers of 3 to the nearest power of 2.
The name, in keeping with ntiscifer, comes from one of Vector's fictional settings, this time "Tervenna". It ultimately derives from a conlang Vector made.
See 9th-octave temperaments for technical data.