As hinted in the description, ("He was the 64th Tribal Chief"), the text is base64 encoded.

Decode the message:

```
$ echo "TWVyY3VyeVZlbnVzRWFydGhNYXJzSnVwaXRlclNhdHVyblVyYW51c05lcHR1bmU" | base64 -d
MercuryVenusEarthMarsJupiterSaturnUranusNeptune
```

flag: Trollcat{MercuryVenusEarthMarsJupiterSaturnUranusNeptune}