royal vs royal stag

royal and royal stag both are nouns.

Word	Noun	Adjective	Verb	Adverb
royal	Yes	Yes	No	No
royal stag	Yes	No	No	No

As nouns, royal and royal stag are synonyms defined as:

royal (noun)	royal stag (noun)
stag with antlers of 12 or more branches	stag with antlers of 12 or more branches
a sail set next above the topgallant on a royal mast

royal (adjective)	royal stag (adjective)
of or relating to or indicative of or issued or performed by a king or queen or other monarch
established or chartered or authorized by royalty
invested with royal power as symbolized by a crown
being of the rank of a monarch
belonging to or befitting a supreme ruler