Pillow Fort decks protect themselves with permanents that discourage or restrict attacks rather than continually destroying opposing creatures. The resulting defenses make attacking you expensive, ineffective, or simply less appealing than attacking somebody else.
Windborn Muse puts a Ghostly Prison-style tax on a creature, while Crawlspace limits the number of attackers that can come your way. Commander decks can then use politics or slower win conditions from behind their increasingly comfortable walls.