No idea.
I bought the game in october and just started playing it tonight. Also went into this blind outside of looking at random DLC crap.
Well, Red Midna and any Ghirahim outfit isn't dumb.
Ok I will explain it.
1. In Legend Mode Link will get the Master Sword. It has a 25000 affix on it. It's locked till you earn every single weapon in the first adventure map. That's all on them, even the Lv2 and Lv3 versions. But just that one adventure map.
2. Once that is done you can start to get 25000 KOs with the master sword. That will unlock the ability and give the Master sword 200 more damage. For a total of 500 damage.
3. Once this is done then all the other 25000 affixes you get on other weapons will unlock. You still need to get 25000 KOs for each one. Just in the same way you got the 1000 KOs to unlock that one. Same deal here bot 25000KOs.
4. Once it is unlocked on other weapons it's active. What it does is a little strange. It makes the base level of any weapon 300 damage before weapon stars. In other words it makes the weapon slightly better than a Lv3 weapon. You still need 5 stars to get the max damage though.
So if you put the Legendary Affix (that it's called once you get the 25000 KOs on any 5 star weapon, Lv1, Lv2, or Lv2, does not matter, that damage will be 450. 30 more damage higher than your Lv3 weapon.
Why does this even exist?
Say you are using a Lv3 weapon cause it's the best damage, but you like the looks of the Lv2 weapon better. Well now you can boost your Lv2 (or any weapon to 450 damage (if it has 5 weapon stars on it). So you can use the weapon you think looks the best and not sacrifice weapon looks.
Just remember you can't remove affixes from weapons only transfer them and destroy the old weapon. Never destroy a weapon with Legendary affix, cause of the 25000 KOs it needed to unlock. Just move it to the weapon you want. I personally tey to make weapons with the following affixes:
Legendary (25000)
+ EXP (to level faster)
+ Rupees (to buy levels and the occasional twilight princess potion faster)
+ Materials (to have a better shot at getting a better material)
I don't think anything else is needed. That 3000 one I mentioned above might be nice but it's not needed and I've never had it to know how effective it is.
If you have any more questions feel free to ask.