Stick was actually the cognitive shadow of a Yolish Lightweaver who was also an electrum compounder, they stole Kenton's stubbornness through a zinc hemalurgic spike, and compounded it, making them the most stubborn being in the cosmere, they were adrift in shadesmar, saw Shallan, panicked, and disguised themself as a stick.
The Seventeenth Shard and Chemoarish, the Dustmother.
Take care to observe that you don't get them mixed up with us, the 17th Shard, I've seen that happen before.