On Kaalann, the Eleventh Doctor collected a Dalekanium coil and a Kontron crystal, using them to construct a chronon blocker to stabilise Amy Pond, who she had became a temporal paradox and started to fade after the Daleks altered history and exterminated humanity before her birth. The Doctor's TARDIS had the same effect, but that could only last for so long. (GAME: City of the Daleks)