In general, I would look at these two factors when looking to include cards not of your tribe's creature type: Is this creature so strong that it, on its own, is generally stronger than my tribal creatures when they are receiving bonuses and/or empowering my other cards
Even on his stats alone, a 5/4 for four mana with no drawback is extremely good
Chienpao ex has the ability Shivery Chill, which allows players to add two Basic Water Energy from their deck to their hand if Chienpao ex is in the Active Spot
Activated abilities are a huge part of the game across all colors and card types, so the question simply becomes "what can I do with two extra mana each turn?" It could be something as simple as activating Reckoner Bankbuster or an incubation token, or maybe something else entirely
Rhystic Study hasnt been heavily printed in quite some time, but it did used to be a common, and there are quite a few copies from Prophecy still kicking around out there