Yorkville accumulates shares at a 10% discount of the trailing vwap. Quick runups like this are perfect selling opportunities for them, that's why none of these rallies sustain themselves lately.
On Oct. 25th niocorp rallied to $5.18 but the trailing vwap was weak so the very next day Yorkville was able to get 228,861 at $3.44 each to sell, thus killing the rally. Down $1.50 to $3.68 by Nov. 6th.
Yorkville makes charting fruitless at this point imo but maybe they'll settle their debt this quarter.