As hinted in the description, ("He was the 64th Tribal Chief"), the text is base64 encoded.
Decode the message:
```$ echo "TWVyY3VyeVZlbnVzRWFydGhNYXJzSnVwaXRlclNhdHVyblVyYW51c05lcHR1bmU" | base64 -dMercuryVenusEarthMarsJupiterSaturnUranusNeptune```
flag: Trollcat{MercuryVenusEarthMarsJupiterSaturnUranusNeptune}