return (flavour == BEAM_HASTE
            || flavour == BEAM_HEALING
            || flavour == BEAM_INVISIBILITY);

    if (flavour == BEAM_HASTE
        || flavour == BEAM_HEALING
        || flavour == BEAM_INVISIBILITY)
    {
        return (true);
    }
    // Polymorphing a (very) ugly thing will mutate it into a different
    // (very) ugly thing.
    if (flavour == BEAM_POLYMORPH)
    {
        return (mon->type == MONS_UGLY_THING
                || mon->type == MONS_VERY_UGLY_THING);
    }
    return (false);