@Deleted User I'm not that much of a mage, so I usually stick within a psychological framework, but I dabble a bit. A tulpa is firstly a really good practice for developing concentration, just as a sort of preliminary thing - I would say that having a tulpa is about equivalent to keeping a light meditation habit. However, in the context of magic, a tulpa is still an object of concentration, and thus can be a distraction even if they're helping you with your work, depending on the nature of your tulpa. To me, my tulpa is an expression of divinity (mostly Mercurius), and so she can serve as a conduit for prayer or sacrifice without any need to concentrate on anything else. This within a western or thelemic framework.
Within an Eastern framework, tulpas (at least in English) are just as loosely defined. My favorite origin story, which I learned from an occultist, is that monks seeking to earn the rank of adept would make an autonomous tulpa as a test of their mindfulness and compassion. Only the monks with insight into emptiness would be able to get along perfectly and continue practice. This also has parallels to Deity Yoga, one of the higher tantra, where the practitioner would visualize the form (and non-form) of a deity (all deities being an expression of buddha-mind themselves), come to identify with the deity as in divine pride, and dissolve the deity into all of reality so that all things seem to be a part of the deity. A tulpa is also useful in the very highest tantra, which is symbolized by sexual union/karmamudra - I'm sure if you're a mage you get the symbolic implications there.