Complex sentence: Over the course of their travels, Talion and Celebrimbor have multiple encounters with Gollum, who has the ability to see and speak with Celebrimbor due to his prior contact with the One Ring.
Split into simpler sentences: Over the course of their travels, Talion and Celebrimbor encounter Gollum multiple times. Gollum possesses the ability to see and speak with Celebrimbor due to his prior contact with the One Ring.