Cleidomancy
It’s a divination form using a key suspended by thread as a medium, the key held between thumb and forefinger. On being lowered into a glass and a question asked, the key would tap once on the side of the glass for a positive answer and twice for a negative.

Cleromancy
It’s a divination form using the casting of lots or another stuff which is similar to dice such as pebbles or sea shell.

Coscinomancy
It’s a divination form using a hanging sieve as a medium. This divination apparently used to identify the perpetrator of a crime. See Radiesthesia.

Critomancy
It’s a divination form using barley cakes as medium.

Cromniomancy
It’s a divination form using onion sprouts as medium.

Crystallomancy
It’s a divination form through crystal gazing such as quartz, precious stones (esp. beryl) or the traditional 'crystal ball'.

Cyclomancy
It’s a divination practice by the study of a turning wheel