Cawl, Dominatus Dominus

Canticle (You may tap this creature. If you do, you
gain 1 counter of Maintenance, then trigger any
relevant Canticle effects. All counters of Maintenance
are sacrificed during the end step.)
Once you have 4 or more Maintenance counters,
add {c}{c} and draw 2 cards.
Once you have 8 or more Maintenance counters,
the next 3 artifact spells you cast this turn you
may cast without paying their mana cost.