Sephera, Nightgear Mechanic

At the beginning of your second main phase each
turn, look at the top three cards of your library.
You may exile an artifact card from among them
face down, and put the rest at the bottom of your
library in any order. If you do, put three Weld
counters on it.
{b}, {t}: Remove a Weld counter from a face down
card in exile. When the last is removed, cast it
without paying it's mana cost.