Protoctists?

[Midson]

There are definitely multi-celled Protists, and it is not a kingdom, it is a group of kingdoms. Within it are lots of different organisms but the taxonomy of them is debated. There are Chromalveolates, Rhizarians, Excavates, Heterokonts and Alveolates but Heterokonta might be within Chromalveolata. Sometimes the last 4 are considered kingdoms but theres loads of different theories