Chamber Sentry enters and dies as a state-based action due to having 0 toughness, triggering Mortuary and Moldervine Reclamation.
Resolve the Mortuary trigger, putting Chamber Sentry from your graveyard onto the top of your library.
Resolve the Moldervine Reclamation trigger, causing you to draw a card, thus drawing Chamber Sentry from your library, and gain 1 life.
Repeat.
This clever little loop turns a tragic fate into a perpetual motion machine by casting Chamber Sentry for zero mana, allowing it to instantly crash into the graveyard and trigger Moldervine Reclamation to draw you a card while gaining life. Simultaneously, Mortuary intercepts that trip to the graveyard by placing the Sentry right back on top of your library, making sure it is immediately waiting for you to draw again. Together, these two enchantments turn an unassuming construct into an endless engine for life, draws, and storm count.