System's Twilight Hint Guide:

Underground River

I don't know how to get to the words that the gates want.

• SOVEREIGN -> SOVERE -> RESOVE -> ROSEVO -> ROSE -> ROZE -> ZERO
• SEA -> SEEAA -> SE -> SEE -> SOO -> ZOO
• DIME -> PENNY -> PEONY
• TEN -> ONE -> OONEE -> OONE -> PONE -> ONEP -> HONEP -> PHONE
• STUMBLE -> UMBLEST -> UMBLE -> HUMBLE
• ABBEY -> ACBEY -> ACBE -> BEAC -> HBEAC -> BEACH
• SLATE -> ATESL -> ATE -> AATEE -> ATEEA -> ATFEA -> ATFE -> FEAT