break;
    case CLOUD_MUTAGENIC:
        which_colour = ETC_MUTAGENIC;

        // Maybe we'll get a mutagenic cloud.
        if (coinflip())
        {
            beem.effect_known = true;
            tracer_flavour = beem.flavour = BEAM_POTION_MUTAGENIC;
            break;
        }
        // if not, deliberate fall through for something random

        break;
    case CLOUD_MUTAGENIC:
        simple_monster_message(monster, " is engulfed in a mutagenic fog!");
        // Will only polymorph a monster if they're not magic immune, can
        // mutate, aren't res asphyx, and pass the same check as meph cloud.
        if (monster->can_mutate() && !mons_immune_magic(monster)
                && 1 + random2(27) >= monster->hit_dice
                && !mons_res_asphyx(monster))
        {
            if (monster->mutate())
                wake = true;
        }

    BEAM_POTION_MUTAGENIC,

    BEAM_TORMENT_DAMAGE,          // Pseudo-beam for damage flavour.

    BEAM_TORMENT_DAMAGE,          // 60: Pseudo-beam for damage flavour.

    BEAM_STEAL_FOOD,              // 60: Pseudo-beam for harpies stealing food.

    BEAM_STEAL_FOOD,              // Pseudo-beam for harpies stealing food.

    CLOUD_MUTAGENIC,

--     grey smoke, blue smoke, purple smoke, steam, 
--     foul pestilence, black smoke, thin mist (the default).

--     grey smoke, blue smoke, purple smoke, steam,
--     foul pestilence, black smoke, mutagenic fog, thin mist (the default).

#include "mutation.h"

    case BEAM_POTION_MUTAGENIC:
        return CLOUD_MUTAGENIC;

    case CLOUD_MUTAGENIC:   return BEAM_POTION_MUTAGENIC;

        break;
    case CLOUD_MUTAGENIC:
        mpr("You are engulfed in a mutagenic fog!");
        if (coinflip()) {
            mpr("Strange energies course through your body.");
            if (one_chance_in(3))
                you.mutate();
            else
            {
                give_bad_mutation();
            }
        }

    case CLOUD_MUTAGENIC:
        return (you.can_mutate());

    case CLOUD_MUTAGENIC:
        return "mutagenic fog";

        case BEAM_POTION_MUTAGENIC:

    case BEAM_POTION_MUTAGENIC:     return("mutagenic fog");