You can make one seven lettered word from these letters which is nirvana.
outside
chrisms
minimum
cabbage, baggage
Olympic
outside
You can make two 7 letter words : COSTARS and CASTORS
Germany
lidless
Demented
netball
choanae
stammer
laminae
Wiriest
chrisms
No 7 letter words, the longest is 6 letters, purist