Hi davide,
Welcome to the forum and congrats for your first post.
Short answer:After moving the dragon, it is not removed from the board. It stays on last tile it visited until a new volcano tile or a new dragon tile is placed. The volcano tile will move the dragon to a new location and the new dragon tile will allow the dragon to move again up to 6 tiles starting from the current tile it is on.
Long answer:The dragon stays out of the game until the first volcano tile is placed. At that point you place the dragon on the volcano tile.
Notes:* If before that point you draw a dragon tile, you put it aside until the first volcano tile is drawn. Then you mix all the dragon tiles put aside with the rest of the tiles.
* If playing with River II, you will not have this issue as the lake tile of this river features a volcano.
After placing the volcano tile and the dragon on it, there are two possibilities:
1) A player draws a dragon tile: in this case, the dragon moves from its last position (a volcano tile recently placed or the last position of a previous dragon movement).
2) A player draws a volcano tile: in this case, the dragon is moved to this tile.
So as you can see, the dragon can move several times without placing a volcano tile. If a player places a dragon tile, the dragon moves six tiles, if possible. And later, if another dragon tile is placed, the dragon moves six tiles again, if possible. The dragon is not removed after its movement finishes. It just stays there until the next dragon tile or the next volcano tile is drawn and placed.
You may check the rules here:
*
http://wikicarpedia.com/index.php/The_Princess_and_The_Dragon#The_dragon:_volcano_and_dragon_symbols_.5B4.5DHope this helps.
Cheers!