My record so far isIn my second full run of the Spire since the bear artifacts have been available, I received 2 artifacts, one at the second to the last boss and one in a purple mystery chest. I had hopes at the last boss, but alas just another Dwarven Armorer. I do have six of those now. When I get to 50 or so, maybe I will use them.
My record so far is:
Week 1 0
Week 2 2
...more like took pity on how you've had your 1 championship, and now get to endure the next 50 years of;2 purple chests and a brown in my first 5 battles this morning (wat?) and purples both gave artifacts
first floor boss also gave up an artifact
so three on the first floor brings me to six total
it's like rngesus saw my event run and took pity on me