Dissolution music from Nihil mission in "Metal: Hellsinger" game.
(Control/Anticipation/Assault): https://www.youtube.com/watch?v=FTQ5akx7syQ
(Stealth): Stealth is from various story cutscene musics of the game. https://www.youtube.com/watch?v=incfWbas91A (5:43 - 6:27, 6:47 - 7:27, 17:58 - 18:54)
if you don't like using CustomOST and prefer using BeardLib, i suggest using this mod to convert CustomOST into BeardLib supported mods. https://modworkshop.net/mod/40369