Dwarf star alloy

From TARDIS Index File, the free Doctor Who reference.

Dwarf star alloy was an alloy. It was obtained from white dwarf stars. It was the only material that could hold Time-sensitive species.

It is very expensive and very heavy.

Rorvik's space ship was made from Dwarf star alloy and required very large engines to move the ship. (DW: Warriors' Gate)

Father of Mine was chained with a chain made from Dwarf star alloy. (DW: The Family of Blood)