How I Made My Katarina Weapons

Daggers

I made Katarina's daggers completely out of craft foam. 
Now I will note these aren't 100% perfect, nor the way I would've liked them to turn out, but with what I had to use and the time I had left (I procrastinated) it's what I could do. I'm still happy enough with them though.

---

I drew the basic shape of the daggers onto a piece of paper, then traced it onto a thin sheet of craft foam -I made 6 daggers and layered together 5 pieces of these shapes for each, so about 30. Cut those out. I drew only the bottom half of that shape 6 more times onto what I had left of a thick piece of craft foam. I glued the 5 thin pieces all together and tried my best to cut it all the edges at an angle, so that the middle piece would be the longest point-like a blade. Then I cut all the edges of the thickest piece of craft foam at an angle -it would've looked better had I cut them at even more of an angle than what I had. Glue that onto the top of the 5.
Using a reference photo, I traced out similar designs as on Katarina's daggers, onto the front of mine.
So note, I originally used magnets to attach the daggers, small circular ones. So at this point, I outlined the shape onto the center back of each dagger and cut out about 2 layers (of the 5 thin pieces of craft foam). I'll mention now, the magnets worked fine, but for larger cons I wouldn't recommend, while they held fine when moving about they would've easily had gotten knocked off if hit against something/one. I ended up super gluing them for the con, but either a stronger magnet or attaching belt-like holders would've worked as well.

---

After this I primed them (with wood glue), then spray painted them with metallic silver spray paint (acrylic paint would work too). Now shade and highlight (I used oil paints to do so, but acrylic would work as well). Lastly, I glued the magnets onto the back of the dagger and spots on the thigh-belt where I wanted the daggers to sit.

---

Swords/Blades

For her swords, I used expanding foam, cardboard, craft foam, fabric, and wood. 
To start off I traced the shape of her dagger onto a piece of cardboard then (make 2). I covered one side of both of them in expanding foam, let that dry then do the same to the other side. 
I also took a long thing wooden post (from Walmart) and cut that into the appropriate size -this is up to you. I had no exact measurement, I just eye-balled it and went with what looked right. 

---

Once everything was dry, using a knife (I believe it was a steak knife-one with teeth) and a box cutter, I started shaping it. I cut off all the excess around the sides of the cardboard, then angled both sides so that they would come to a point where the cardboard was- think like a blade. Of course, I kept that oval part at the bottom wider than the blade. I also flattened out/evened the top of each half. Use a reference picture to figure out the exact shape of everything. 
I then took pieced of craft foam and covered the sword. You can see some of the shapes I cut of craft foam here. I also took another small piece of craft foam and wrapped a strip around the bottom of the wooden post.
To attach the wooden post, I outlined the size after figuring out where I wanted it -centered as best as possible- and cut out about an inch or so, then glue it in place (with super glue, hot glue and wood glue -I wanted it to stay).

---

I took thin, long strips of craft foam and glued it around the edge of the top part of the blades-like outlining it. 

Using a reference photo, I traced out shapes, that looked similar to the design in the photo, onto a piece of paper and used that to trace the same shapes onto craft foam (4 times). Cut those out. To figure out the size, I just would eye-ball it then place it onto the blade and change it as needed (when using the paper).  Glue those in place. It should look the same on all 4 sides.

---

Now prime and spray paint everything. I used metallic silver paint. 
Once everything was dry I when ahead and cut out long strips (ribbon could work too) of brown leathery(semi-velvety but not ~I don't know the name of the fabric) like fabric and wrapped it around the wooden handles. Glue it into place -so glue it at both ends and randomly around the middle. 
Using oil paints, I shaded and highlighted everything. 

---

Other Swords

I don't have any real good photos. But as for the swords on the back and side: I made those literally the day before (super bad with procrastination!). Sorry to say, but I just ran to the $1 Store and bought some foam swords in a shape that I liked -I was lucky to find the exact shape and size I wanted (had to go to a few different stores). I used black electrical tape to wrap the blade part -it gave the effect I wanted. For the handled I used the same fabric as on the other two swords (^ up there) and painted the very end a metallic grey. Had I had more time (and money for more expanding foam), I would've used the same technique as I did for the main swords -cardboard and expanding foam- and used this same shape. Still probably would've wrapped it with electrical tape or fabric since, according to the reference photos I had, they looked sheathed. 

And finished! Hope I could help and that my explanations were good enough >.< 

~Positive outcomes only! :)