Had an idea, somewhat similar to this, when reading through the Pathfinder rules (yeah, yeah, inb4 and all that shit, whatever) when a friend wanted to run a game that never actually got off the ground.
Basically, the idea went something kind of like this: Summoners are pretty much defined by their ability to create Eidolons - or in this instance, Tulpas. Tulpas, in turn, are defined by their ability to be, as it were, defined by their Summoner.
A Summoner puts a lot into their Tulpa, in order to craft it. Arcane power is just the start; a true Tulpa is more than just another summoned creature after all. Will, motive, drive - these fuel it, give it reason, give it ability to act and develop and grow.
Most Summoners are pretty satisfied there; some, however, go further with it. Emotions, desires, even memories are given to the Tulpa, increasing its power and its ability to sustain itself, to become more 'real'.
In the end, though, only one thing alone can sustain a Tulpa past the end of its Summoner's own life, and rare indeed is the Summoner willing to gift such a precious thing as that, even to their own creation.
Rare, but not impossible.
With this final gift, given freely as the Summoner's last act, the Tulpa is at last Unfettered. While not as strong as before - relying on the power of one instead of two is a limiter, after all - the newfound freedom is still one most would consider worth the price.
And with this newfound freedom, this newfound life, comes an equally new, exciting and terrifying possibility - the chance that they might, in turn, learn to create life of their own.
Like I said, it was an idea, and one that never got off the ground. Probably for the best, but eh.
Anyway. Back to feckin' off. Feel free to ignore my rambling.