One of my players has expressed interest in playing as one of the villains as a pc after hes redeamed and had curses removed, stuff like that, but his attacks and such dont fit into any sort of dnd class.

His fight is that he has been soul linked to a feycursed tree, and so has things like wood and bark skin and can manipulate his arms to create his own wooden weapons and grapple tools, if this is anything like another subclass of something please let me know, but if its not imma need some more ideas for the class since ive never done a full hb class before.

For reference, the character will be fought at around level 6, and the main weapons he uses are polearms and a greataxe

In dnd beyond? Or in general, because currently you can't homebrew classes in dnd beyond and you have to make the class from scratch.

I just mean in general since i usually do hb spells and stuff in my notebook

If it were me, I would do one of the following two things instead of writing a whole class just for the one character:

1. I would probably be considering creating it as a Druid subclass instead of as a whole class. I would be taking inspiration from subclasses like Circle of Stars, Circle of Spores, & Circle of Wildfire for ways to create a feature that works like  Starry Form, Symbiotic Entity, and Summon Wildfire Spirit to write a feature that starts off something like “As a bonus action, you can expend one use of your Wild Shape feature to….” That would be muu—uuch simpler than writing a whole class.
2. I would create a homebrewed Race that did the whole tree thing and then let them play a regular class like a Fighter.

Just some alternative ideas to consider.