Sentry Conduit

Guards your yard with a lens: casts at monsters within 12 blocks; with a Mend lens it heals your wounded instead — players, tamed animals, villagers. Pays flux from its own chunk like your casts and never changes blocks. Sleeps while no player is within 64 blocks or under a redstone signal. Use a cut lens on it to set it; sneak-use empty-handed to take it out.