There is a post here in which a player has a screenshot of a level 20 Moa Bird. Just a plain Moa Bird...no "hearty" or "dire" or anything. I didn't think much of it at the time, but then it happened to me as well.
I've been trying to train a Melandru's Stalker with the "aggressive" prefix. This particular stalker is my fifth or sixth pet; all the others became "playful" at level 11. However, the current one is up to level 13 and has no prefix whatsoever. I have treated them all in more or less the same way: 16 Beast Mastery, carrying a sword instead of a bow, and using pet attacks exclusively. The only difference I can think of is that so far this pet hasn't died at all.
If anyone has a similar story, or an insight as to why pets turn out this way, I'd be interested in hearing it.
Pet prefixes (or lack thereof)
October Jade
Epinephrine
I'm that player (Moa Bird); I have since also raised a type-less Dune Lizard to level 18, he'll hit level 20 tonight and I'll finish testing him then.
I don't know exaclty what the trigger is, it may be that the pet hasn't suffered enough damage, or died enough to get the "playful", and yet hasn't inflicted enough damage (or has taken too much, or died too much*) to get "aggressive".
If it makes you feel any better, the typeless pets seem to be equivalent to Elder pets, at least by our (Jenosavel and my) first tests. Just no title.
*obviously not yours, but deaths seem to be a factor
I don't know exaclty what the trigger is, it may be that the pet hasn't suffered enough damage, or died enough to get the "playful", and yet hasn't inflicted enough damage (or has taken too much, or died too much*) to get "aggressive".
If it makes you feel any better, the typeless pets seem to be equivalent to Elder pets, at least by our (Jenosavel and my) first tests. Just no title.
*obviously not yours, but deaths seem to be a factor