void main()
{
    object oArea = GetArea(OBJECT_SELF);

    // If the entering creature is an undead and not a player
    if (GetRacialType(OBJECT_SELF) == RACIAL_TYPE_UNDEAD && !GetIsPC(OBJECT_SELF))
    {
        effect eUltravision = EffectUltravision();
        eUltravision = SupernaturalEffect(eUltravision);
        ApplyEffectToObject(DURATION_TYPE_PERMANENT, eUltravision, OBJECT_SELF);
    }

    // Set area parameters
    SetLocalInt(oArea, "nMonChance", 30); // 30% chance of rest being interrupted
    SetLocalString(oArea, "sMonster", "nw_skelwarr01"); // Monster blueprint or "CUSTOM"
}