So, first thing to know, a woodland mansion is a 3 story house and it is located in the dark oak forest. It is made of the dark oak wood. There are Vexes, Vindacators and Evokers. These mobs are dangerous.
How to find a Woodland Mansion
To find this structure, you will need to find a cartographer villager. They look like a normal librarian but when you trade with them, they will show cartographer as the name and you will need to trade with them a lot just to get a Ocean Monument or a Woodland Mansion map.
In the first level of the Woodland Mansion, you will only find Vindacators . This is because they are "weak". They hold
iron axes, so you might want enchanted diamond armor. You can find treasure he as well. They drop Emeralds and xp.
In the second level, you will find Vindacators and Evokers. Evokers will drop Emeralds, a Totem Of Undying and some xp. Be careful while you try to kill the Evokers because they will spawn Vexes. Vexes have a iron sword and they can fly. They are basically ghost because they also go through walls. Another attack Evokers do it that they spawn spikes to eat you. This level also has some treasure.
This level has Evokers and Vindacators as well. This level is the last level and it is smaller.