The answers to the clues below will have something in common.

1. Start knitting
2. Set sail
3. Metaphor for crowds of people
4. Shipwreck survivor, perhaps
5. "The decision has been made."
6. Unchangeable
7. Enchant, metaphorically
8. Illuminate
9. Impugn
10. Vote
11. Construction or stomach material
12. Biblical command to accusers of adulteress

Answers:

1. Cast on
2. Cast off
3. Cast of thousands
4. Castaway
5. "The die is cast."
6. Cast in stone
7. Cast a spell
8. Cast light on
9. Cast doubt on
10. Cast a ballot
11. Cast iron
12. "Let him who is without sin cast the first stone."