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 (image):
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*