Westvale Cult Leader's power and toughness are each equal to the number of creatures you control.
At the beginning of your end step, create a 1/1 white and black Human Cleric creature token.
(08/04/2016)
If you don't control four or more creatures as Hanweir Militia Captain's ability resolves, it won't transform.
(08/04/2016)
Once Hanweir Militia Captain has transformed into Westvale Cult Leader, controlling fewer than four creatures won't cause it to transform back.
(08/04/2016)
If you don't control four or more creatures (including Hanweir Militia Captain itself) at the moment your upkeep begins, its ability doesn't trigger. You can't wait for other effects in your upkeep to provide creatures.
(08/04/2016)
Westvale Cult Leader's first ability counts itself, so it will normally be at least 1/1.
