return (testbits(mon->flags, MF_ENSLAVED_SOUL)
        && mons_holiness(mon) == MH_NATURAL);

    return (mon->has_ench(ENCH_SOUL_RIPE));

        }
        break;
    case ENCH_SOUL_RIPE:
        if (!quiet)
        {
            simple_monster_message(this,
                                   "'s soul is no longer ripe for the taking.");

        case ENCH_LOWERED_MR:

        case ENCH_LOWERED_MR: case ENCH_SOUL_RIPE:

    case ENCH_SOUL_RIPE:

    "decay", "bug"

    "soul-ripe", "decay", "bug"

    ENCH_SOUL_RIPE,

                                     // Yredelemnul's power, or the natural
                                     // monster from whom the soul is taken

                                     // Yredelemnul's power

Mark a monster's living soul as ripe for the taking. Once the marked monster dies, its soul will be yours.

Mark a monster's living soul as yours, once the monster dies. The soul will retain at least some of the monster's innate healing ability and faculties, and sometimes even the monster's equipment. However, you can only enslave one soul at any given time. Note that enslaved souls, whether twisted or intact, can follow you beyond the level they were created on.

The soul will retain at least some of the monster's innate healing ability and faculties, and sometimes even the monster's equipment. However, only one soul can be enslaved at a time. Also, only a relatively uninjured monster can have its soul marked, and the duration of the mark is dependent on Invocations skill.
Note that enslaved souls, whether twisted or intact, can follow you beyond the level they were created on.

    {

        if (mon->hit_dice >= random2(ench_power / 2))
            return (MON_RESIST);

        // The monster can be no more than lightly wounded/damaged,
        // using the formula from monstuff.cc:mons_get_damage_level().
        if (mon->hit_points <= (mon->max_hit_points * 3) / 4)
        {
            simple_monster_message(mon, "'s soul is too badly injured.");
            return (MON_OTHER);
        }

        mon->flags |= MF_ENSLAVED_SOUL;

        const int duration = 1 + you.skills[SK_INVOCATIONS] / 2;
        mon->add_ench(mon_enchant(ENCH_SOUL_RIPE, 0, KC_YOU, duration * 10));

    }