By-products. Of processes. That are perfectly safe.
This six-sided die warns of a biological hazard. It's mathematically safe, though, designed for symmetry and fairness. Use it for rolls involving mutants, zombies, or plagues, or just for anything that's totally sick.
Spell damage dice: Acid d4 | Psychic d4 | Fire d6 | Lightning d6 | Acid d6 | Radiant d6 | Necrotic d6 | Psychic d6 | Sonic d6 | Cold d6 | Radiant d8 | Cold d8 | Lightning d8
Weapon damage dice: Dagger d4 | Mace d6 | Arrow d6 | Short sword d6 | Quarterstaff d6 | Spear d8 | Arrow d8 | Battleaxe d8 | Longsword d8 | Mourningstar d8 | Greataxe d12
Mana symbols: White | Blue | Black | Red | Green
Seasons: Spring | Summer | Fall | Winter
Sports balls: Football d4 | Baseball d6 | Basketball d8 | Hockey d10 | Badminton d00 | Volleyball d12 | Soccer d20
Flowers: Daisy | Daffodil | Lily | Hibiscus
Symbols: Atom | Radiation | Biohazard | Laser | Fallout shelter | Recycling
The Dread Gazebo: d4 | d6 | d8 | d10 | d12 | d20