Level   Ecks       Sever 
2       EXTREME    SEVERE 
3       EXCITE     SURVIVE 
4       EXCAVATE   SAVANT 
5       EXCALIBUR  SUFFER 
6       EXTORT     SULPHER 
7       EXPIRE     SERVE 
8       EXACT      SEETHE 
9       EXHALE     SEVERAL 
10      EXHUME     SEVERANCE 
11      EXONERATE  SAVAGE 
12      EXPEL      SACROSANCT  

Thanks to Revolution readers razorz_edge, Matty McC, and Scott Bodders!