Goblins have their Conspicuous Snoops, green tribes have their Allosaurus Shepherd, zombies get to run cards like Zombie Apocalypse, etc
It doesnt have quite as much board impact as Nightpack Ambusher, but I think Enduring Curiosity does enough to fill that role if you build to optimize it with small evasive guys
Crab might seem odd here, but we have a lot of ways to get lands into play from our library, so it turns cards like Crop Rotation, Harrow, and Growth Spiral into mill spells
Defend the Hearth sees competitive metagame play in 1 format(s): Commander
Specifically, unless Space Beleren's first loyalty ability has been activated, sector assignments have no effect on combat