From mer- + guard.
merguard (plural merguards)
- (fantasy) A merperson guard.
1999, Bobbi J. G. Weiss, David Cody Weiss, Age of Aquariums, Archway Paperback, →ISBN, page 133:He and his merguard surrounded her before she could say a word. "What kind of Conch Queen of Doom are you?" he griped, angrily jabbing at Sabrina with his trident.
2009, Delia Sherman, The Magic Mirror of the Mermaid Queen[1], Viking, →ISBN:Two muscular merguards twisted my arms behind my back and tangled my legs in seaweed.
2011, L-J Baker, Promises, Promises, Lethe Press, →ISBN, page 148:Mer-guards flanked the front opening to the palace.