Originally Posted by
Kyeudo
You do it the same way you make any other non-standard item: Homebrew. See, we have the origional item itself, which is decidedly non-broken. Then we have the general guideline for grafts (it's not given, but reverse engineering has shown that they stay pretty close to twice the cost of a normal magic item that could do the same thing). Putting the two together gives us the double costed, but unlosable Silver Tongue.
Depending on which Graft Flesh feats you have access to, I recomend putting it in the Silithar, Warforged, or that other type of construct graft availible (I forget their name), but making a graft from the tongue of a Logokron Devil would work for a Fiendish graft.