The theme is

>! Monsters from the 2nd edition of Dungeons and Dragons. Specifically, they come from the Monstrous Compendium Volumes One and Two.  
>!  
>! As for the title... OP said there was no special meaning behind it. :P  

Clue explanations:

>! 1\. **GNOLL** = LONG< + L\_  
>! 2. **LICH** = \_LIC H\_  
>! 3. **BEHOLDER** = B(HE<)OLDER  
>! 4. **SHAMBLING MOUND** = SHAM + BLING + M\_ O\_ U\_ N\_ D\_  
>! 5. **XORN** = XOR + N  
>! 6. **OTYUGH** = TO(\_Y)UGH\*  
>! 7. **ANKHEG** = ANKH + EG\_  
>! 8. **BULETTE** = BU(L\_E)TTE  
>! 9. **GELATINOUS CUBE** = \_G + LATE< + COUSIN\* + UBE(-r)  
>! 10. **SAHUAGIN** = IG(\_H\_)UANAS\*