#[I've mentioned Zwei alerting in a couple of threads so here's this headcanon]

[unlockthestars]

Tai deals with severe depression, which would likely be classified as MDD (major depressive disorder). It's something he's struggled with pretty much all of his life, but by far the worst two periods were after Raven left and after Summer died.

In both instances, he went practically catatonic, not moving or speaking, barely doing the minimum needed in order to keep himself alive, and only that because there were other people around.

Summer and Qrow helped take care of baby Yang…., and then after Summer died…., Tai knows that he dropped the ball, that Yang, young as she was, had to pick up the pieces.

The day that Qrow saved Yang and Ruby from a Grimm attack was something of a wake-up call for Tai, and he started actively working on managing his depression. He started therapy, and working through things.

That's also where Zwei comes in. He's more than just a pet; he's Tai's service dog. Zwei helps to keep him calm as needed, and he's also trained to pick up objects and bring them to Tai, as well. Additionally, he'll alert if Tai starts to exhibit any dangerous or harmful behaviour, for example.

Tai's doing a lot better, but he's still aware of just how bad he can get, and he's doing his best not to allow himself to get that bad again.