Unicorns drop "horncore" every 5 min in real time and you can use this item to craft everything else.
Harvesting them will take some time but you can breed unicorns to get more and make like a farm but make sure you put a leash on it otherwise it will fly away.
Unicorns are tameable but not ridable they are like wolves they attack mobs the player attacked only if they are untamed or mobs who attacked the player and they barely get damaged.
To breed or tame unicorns you have to get a crystal apple from a special tree and to get that tree you have to plant an oak tree sapling then right click it with horncore and yes it only works on oak saplings.
Also this tree gives you a few blocks to make and decorate with it, and you can craft with coreoak planks a special bookshelf that gives you 6 enchantment power to the enchanting table which means you will only need 5 of them to reach level 30.
Remember when crafting the bookshelf to choose from the menu the special one (wine colored).
There is also a few blocks you can make with amethyst blocks and horn core and they glow in the dark.
You can also make tools that are stronger than netherite with horncore and amethyst shards and make armor with horncore.
Also brewing horncore into an awkward potion gives you a special potion which is beneficial.
Last but not least you can craft a special feather with horncore that gives you feather falling and jump boost as long as it's in your hand.