Here's an idea sprung from a discussion on this week's critical role. I thought it was novel enough to share.
Wikipedia tells me that pine tar was known to the ancient Greeks and was a primary export of 14th century Sweden. I'll then deduce it was known in period.
Moderately Sized Blob of Tar
R: Voice, D: Diam, T: ind (+1 size)
This spell produces a blob of pine tar a bit over a pace in diameter. With a successful targeting role it can placed around a moving target, typically immobilizing it. The ease of escaping from such a predicament is left to the storyguide to adjudicate.
base 2, +2 voice, +1 diameter, +1 size
It's not just about immobilization, having a big blob of stiff very sticky stuff I imagine could be useful in a lot of ways, and different than many of the alternatives, also level 10 is doable for a large proportion of magi with spontaneous magic.