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