Where to Catch Type Null in Pokemon Ultra Sun and Ultra Moon
Type Null is an interesting Pokemon as it is a synthetic Pokemon. What this means is that the folks over at the Aether Institute decided they wanted to create a Pokemon and the result was Type Null. How you acquire Type Null has changed since Pokemon Sun and Moon. Here is where to catch Type Null in Pokemon Ultra Sun and Ultra Moon. Wicke
Where to Find Type Null
Type Null can be found on Poni Island just before the entrance to Poni Grove. You will need to have beaten the Pokemon League and have started the Ultra Beast mission in order to trigger the cutscene here.
Catching Type Null
Type Null is not caught, but rather given to you by Wicke. After completing the Pokemon League and undertaking the Ultra Beast mission, you will meet Wicke outside of Poni Grove. Here she will give you Type Null, because you have proven yourself to be strong and powerful trainer. Alongside receiving Type Null, you will also receive a collection of various memories which can change the type of a Pokemon (if held by a certain species).
Find more Pokemon in Ultra Sun and Ultra Moon here