Is it... lag?

I knew my promos were in jeopardy within the first 30 seconds. After loading in to the rift... I couldn't see any of my teammates. Everyone was invisible. No character models appeared, but ability particles (for instance the bond between the Kalista and her support) did appear. In addition, although I was able to issue movement commands and interact with the store, none of my requests went through. 30 seconds in, this corrected itself and I hoped for the best. Not 1 minute later, I walked into my own jungle and watched my healthbar rapidly decrease with no one around me. Unlike my teammates' icons, I saw no enemy portraits on the minimap. Understanding that my game must be lagging, I flashed away from the 5 ghosts haunting our jungle and managed to escape with my life.

This continued in different instances throughout the game. Sometimes time was seemingly frozen, but then character models would sprint around my screen and I found myself dead. On multiple occasions I stood under tower alone, just to be flooded with enemy champions and killed with no warning. I tried a normal game right after and had the same experience.

Is this a common bug that occurs with new patches from time to time? A problem with my internet connection? I've never had it happen before, so I wanted to petition the community to determine what the problem was. Thanks for your valuable time, I appreciate any expertise in the matter.