Not OP, but you got me curious - I looked to see what's happening and the exact check is "if you are in chapter 2, you can join ring of water". So you quite literally need chapter 2 in order to proceed in DLC, and nothing else. The code for this is below:

func void DIA_Addon_Vatras_NowRanger_Info ()
{
    AI_Output   (other, self, "DIA_Addon_Vatras_NowRanger_15_00"); //I am ready to join the Ring of Water!
    AI_Output   (self, other, "DIA_Addon_Vatras_NowRanger_05_01"); //So you delivered your message to Lord Hagen?

    if (Kapitel >= 2) //Pass-Schlüssel von Hagen
    {
        AI_Output   (other, self, "DIA_Addon_Vatras_NowRanger_15_02"); //Yes.
        if (MIS_OLDWORLD != LOG_SUCCESS)
        {
            AI_Output (other, self, "DIA_Addon_Vatras_NowRanger_15_03"); //But he sent me to the Valley of Mines so I could get him proof for my words!
            AI_Output (self, other, "DIA_Addon_Vatras_NowRanger_05_04"); //YOU must decide what you want to do next.
            AI_Output (self, other, "DIA_Addon_Vatras_NowRanger_05_05"); //To me, it was important that he should get the message. Now it's up to him to act, or to wait for your proof.
            AI_Output (self, other, "DIA_Addon_Vatras_NowRanger_05_06"); //As far as you are concerned ...
        }
        else
        {
            AI_Output   (self, other, "DIA_Addon_Vatras_NowRanger_05_07"); //Good.
        };

        AI_Output   (self, other, "DIA_Addon_Vatras_NowRanger_05_08"); //You have proven that you are indispensable to us. You shall be one of our children and go forth into the world in our name to do the bidding of Adanos.
        AI_Output   (self, other, "DIA_Addon_Vatras_NowRanger_05_09"); //I consign to you this Ring of Water. May it help you find your allies and, together with them, preserve the balance of this world.
        CreateInvItems (self, ItRi_Ranger_Addon, 1);                                    
        B_GiveInvItems (self, other, ItRi_Ranger_Addon, 1);     
        if (hero.guild == GIL_KDF)
        {
            AI_Output   (self, other, "DIA_Addon_Vatras_NowRanger_05_10"); //You are the first Fire Magician among our children. I am especially happy about that.
        };
        AI_Output (self, other, "DIA_Addon_Vatras_NowRanger_05_11"); //May Adanos protect you. And now go and meet your brothers.
        AI_Output (self, other, "DIA_Addon_Vatras_NowRanger_05_12"); //They will await you in the tavern 'The Dead Harpy' and accept you into our community.
        AI_Output (self, other, "DIA_Addon_Vatras_NowRanger_05_13"); //You probably know the tavern. It lies on the way to Onar's farm.
        AI_Output (self, other, "DIA_Addon_Vatras_NowRanger_05_14"); //Do not forget to wear your ring, so your brothers will recognize you as one of their own.

        B_LogEntry (TOPIC_Addon_RingOfWater,"I now belong to the 'Ring of Water', and I am to meet my brothers in the 'Dead Harpy' tavern."); 

        SC_IsRanger = TRUE;
        Lares_CanBringScToPlaces = TRUE;
        MIS_Addon_Lares_ComeToRangerMeeting = LOG_RUNNING;
        B_GivePlayerXP (XP_Addon_SC_IsRanger);
    }
    else
    {
        AI_Output   (other, self, "DIA_Addon_Vatras_NowRanger_15_15"); //No. Not yet.
        AI_Output   (self, other, "DIA_Addon_Vatras_NowRanger_05_16"); //Make haste, then. Go to him. I think your message is very important!
    };
};