They Mostly Come at Night

It becomes night as They Mostly Come at Night
enters.

When They Mostly Come at Night enters or
whenever day becomes night, amass Bats 2. (Put
two +1/+1 counters on an Army you control. It’s also
a Bat. If you don’t control an Army, create a 0/0
black Bat Army creature token with flying first.)

"...mostly."