I'm not sure, but try to go at "data\scripts\teleports\GrandBossTeleporters" and open the file "GrandBossTeleporters.java".
If you search for Antharas, you will see this part:
if (st.hasQuestItems(3865))
{
st.takeItems(3865, 1);
GrandBossManager.getInstance().getZoneById(110001).allowPlayerEntry(player, 30);
player.teleToLocation(175300 + Rnd.get(-350, 350), 115180 + Rnd.get(-1000, 1000), -7709, 0);
Not recommended to delete something, but change the quest item with some adena..
I say again, perhaps I'm wrong.. Just give a try..