Koschei/Theta Recs

[x-losfic.livejournal.com]

seagullsong  just asked me for good Theta/Koschei fic and art recs, and I thought hell, let's make it a party post and open it up to the world for great reccebration!

Please post links below! If you can include the title and author, that'd be most excellent--If you could give a short 'why this is so awesomesauce,' it'd be /superlatively/ excellent.

Have at!