Helpful Tips for Gong Relic

Does anyone have any helpful tips for finding the lightning rod zombie? Spent so much time just rounding all the zombies up on round 20 and then teleporting away and running back to pack and the zombie never showed up. Doesn't make it easy to tell him apart from the other zombies since they all look so similar 😭

I decided to end the round and start fresh on 21 and he never showed up again, felt like I was going crazy 😅 Any advice will be appreciated 🩵