private class WatcherTask implements Runnable
    {
        L2Npc npc = null;

        protected WatcherTask()
        {
            npc = L2Npc.this;
        }

        public void run()
        {
            if (npc == null)
                return;
            if (npc.isDead())
                npc.stopWatcherTask();

            // Get all characters in range 900 (should be enough)
            Collection<L2PcInstance> knowList = npc.getKnownList().getKnownPlayersInRadius(900);
            // Get list of known and triggered already players
            FastList<L2PcInstance> watcherList = npc.getWatcherList();

            // Check if all is ok with our knowlist
            if (knowList == null)
                return;

            // If knowlist is empty we can clear watchlist also if its not empty
            if (knowList.isEmpty())
            {
                if (!watcherList.isEmpty())
                    watcherList.clear();

                return;
            }

            // First verify if player on our list is still in range
            for (L2PcInstance player : watcherList)
            {
                if (player == null)
                    continue;
                if (!knowList.contains(player))
                    watcherList.remove(player);
            }

            // Now check know list for new objects
            for (L2Character character : knowList)
            {
                if (character == null || character.isDead())
                    continue;

                final L2PcInstance player = character.getActingPlayer();
                if (player != null)
                {
                    // Player can be invisible
                    if (player.inObserverMode() || player.getAppearance().getInvisible())
                        continue;
                    // Check if player is on our list (was triggered already)
                    if (!watcherList.contains(player))
                    {
                        // Check if we really 'see' our target
                        if (GeoData.getInstance().canSeeTarget(npc, player))
                        {
                            // Add player to list - we need trigger quests only once
                            watcherList.add(player);

                            // Notify quests
                            if (getTemplate().getEventQuests(Quest.QuestEventType.ON_PLAYER_SEE) != null)
                                for (Quest quest : getTemplate().getEventQuests(Quest.QuestEventType.ON_PLAYER_SEE))
                                    quest.notifyPlayerSee(npc, player);
                        }
                    }
                }
            }