Unlock secret missions in Survival mode by performing the following tasks:
1. Take no damage for 1 minute. 2. Take no damage for 2 minutes. 3. Get 5 splatter kills. 4. Get 20 splatter kills. 5. Kill 25 enemies in Berserk mode. 6. Kill 50 enemies in Berserk mode. 7. Step on 20 Boreworms. 8. Step on 50 Boreworms. 9. Kill 10 enemies with body parts. 10. Kill 25 enemies with body parts.