Sif's hair oil is an extraction of fenugreek seeds into high oleic safflower oil as well as propolis a few studies have shown Fenugreek seed extract to be as effective as minoxidil. Propolis is known to thicken and darken the hair at its base.
Safflower Papers https://www.sciencedirect.com/science/article/abs/pii/S0378517322000916 , https://bmcbiotechnol.biomedcentral.com/articles/10.1186/s12896-018-0433-2
Fenugreek Papers https://www.researchgate.net/profile/Sabyasachi-Chatterjee-3/publication/279038848_Fenugreek_Trigonella_foenum_gracum_L_and_its_necessity_A_Review_Paper/links/5589115b08ae347f9bdad2e9/Fenugreek-Trigonella-foenum-gracum-L-and-its-necessity-A-Review-Paper.pdf