Salanar The Horseman  

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There were several things missing:  
1. #include "precompiled.h"<-- it does contains classes like Player, Creature and Unit you need it in each script.  
2. According to coding standarts of SD2 I dont know why each devisee have to have an p on begining so -> pCreature, pPlayer and pUnit.  
3. DoCast was not fitting its also should be shown while compiling the script, so pPlayer->CastSpell(pPlayer, SPELL_RETURN_REALM, false);  
4. Dont forget to close GOSSIP so: pPlayer->CLOSE_GOSSIP_MENU();  
Hope that it does help you good luck  
Full working script based on yours:  

/* Copyright © 2006 - 2009 ScriptDev2 <https://scriptdev2.svn.sourceforge.net/>  
* This program is free software; you can redistribute it and/or modify  
* it under the terms of the GNU General Public License as published by  
* the Free Software Foundation; either version 2 of the License, or  
* (at your option) any later version.  
*  
* This program is distributed in the hope that it will be useful,  
* but WITHOUT ANY WARRANTY; without even the implied warranty of  
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the  
* GNU General Public License for more details.  
*  
* You should have received a copy of the GNU General Public License  
* along with this program; if not, write to the Free Software  
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA  
*/  

/* ScriptData  
SDName: Salaran Horseman  
SD%Complete: 0  
SDComment:  
SDCategory: Salaran Horseman  
EndScriptData */  
#include "precompiled.h"  

#define GOSSIP_RETURN_REALM "I must return to the Realm of Shadows."  
#define SPELL_RETURN_REALM 52693  

bool GossipHello_npc_salanar_horseman(Player* pPlayer, Creature* pCreature)  
{  
if (pCreature->isQuestGiver())  
pPlayer->PrepareQuestMenu(pCreature->GetGUID());  

if (pPlayer->GetQuestStatus(12687) == QUEST_STATUS_INCOMPLETE)  
pPlayer->ADD_GOSSIP_ITEM(GOSSIP_ICON_CHAT, GOSSIP_RETURN_REALM, GOSSIP_SENDER_MAIN, GOSSIP_ACTION_INFO_DEF+1);  
pPlayer->SEND_GOSSIP_MENU(9978,pCreature->GetGUID());  
return true;  
}  

bool GossipSelect_npc_salanar_horseman(Player *pPlayer, Creature *pCreature, uint32 sender, uint32 action )  
{  
if (action == GOSSIP_ACTION_INFO_DEF + 1)  
{  
pPlayer->CLOSE_GOSSIP_MENU();  
pPlayer->CastSpell(pPlayer, SPELL_RETURN_REALM, false);  
}  
return true;  
}  

void AddSC_npc_salanar_horseman()  
{  
Script *newscript;  

newscript = new Script;  
newscript->Name = "npc_salanar_horseman";  
newscript->pGossipHello = &GossipHello_npc_salanar_horseman;  
newscript->pGossipSelect = &GossipSelect_npc_salanar_horseman;  
newscript->RegisterSelf();  
}  

Это исправление для ScriptDev2, только вот как и куда его вставлять, знает ктонибудь? И если можно выложите его в форме патча.