Adjectives

(s)subterranean, subterraneous, ulteriorlying beyond what is openly revealed or avowed (especially being kept in the background or deliberately concealed)“subterranean motives for murder”, “looked too closely for an ulterior purpose in all knowledge” (Bertrand Russell)
(s)ulteriorbeyond or outside an area of immediate interest; remote“a suggestion ulterior to the present discussion”, “without … any purpose, immediate or ulterior” (G.B.Shaw)
(s)later, ulterior, posteriorcoming at a subsequent time or stage“without ulterior argument”, “the mood posterior to”