Diplo is a very fragile and slow creature that spawn in dangerous areas so I recommend you to

1.if you have a argy use it to carry the Diplo away so it doesn't get killed if you don't have a argy just approach it and make it run away from the dangerous area

2.torpor works like this you shoot the creature and for 8 seconds it's torpor will increase but after the 8 seconds it will instantly start to drain the reload on crossbow takes like 4 or 3 seconds I think so after reloading wait a lil and than shoot it

3.when you get it knocked out feed it meat t tame a narco berries to keep it knocked out (you can use anything but I like narco berries because of how quickly and easily they can be farmed)

4.YOU TAMES A DIPLOCAULUS CONGRATS🎉 🎉