I have this and have called the Yag quite a few times. Here's what to expect from it if you really, really want this PITA trophy.
If you use it while not engaged in battle Tsoo Haja will do that battle cry move they have, then disappear.
If you use it while engaged in battle Tsoo Haja will (this is great) use the foot kick move they have, then disappear.
That's it. Every 20 hours you will see it just long enough to do one move. When you see the final cutscenes apparently Tsoo Haja does not like the fact that he has to serve you from time to time, so seeing him leave after "helping" you out so much makes sense.