Henadic Theologian
Legend
They where created in tandem. It wasn't a case of "we made this magic set, why don't we turn it into a D&D set", it was a case of "we have this idea, which we can use for both MTG and D&D". The timing gives it away.
Actually the MtG started like a year at least before the lead Designer on Strixhaven: Cirriculum of Chaos Amanada Hammon was even hired, it was only at a later stage that both were in development at the same time.