Coin has small chance.
Try this chance taken from L2jServer.
Index: dist/game/data/scripts/quests/Q336_CoinsOfMagic/Q336_CoinsOfMagic.java
===================================================================
--- dist/game/data/scripts/quests/Q336_CoinsOfMagic/Q336_CoinsOfMagic.java (revision 7463)
+++ dist/game/data/scripts/quests/Q336_CoinsOfMagic/Q336_CoinsOfMagic.java (working copy)
@@ -356,7 +356,7 @@
final int npcId = npc.getNpcId();
if ((npcId == HARIT_LIZARDMAN_MATRIARCH) || (npcId == HARIT_LIZARDMAN_SHAMAN))
{
- if ((cond == 2) && (Rnd.get(100) < (10.0 * npc.getTemplate().getBaseHpConsumeRate())))
+ if ((cond == 2) && (Rnd.get(1000) < 63))
{
st.giveItems(KALDIS_COIN, 1);
st.set("cond", "3");