Konami has released a number of franchises over the years and two of the most beloved are Contra and Castlevania, and many fans have had fun finding ways to combine the two franchises together, such as through indie game successors like Infernax which has a Contra-style mode hidden in the main game which is inspired by Castlevania, but also from fan mods. Previously, a modder going by I Love Pheromosa released Contravania: Dawn of Sorrow, a mod that brought Tsugu-Min from Contra Rebirth into the inside the DS game and let you run-and-gun your way through a copy of Dracula’s castle.
Now, another modder named ncoz has taken to Castlevania: Order of Ecclesia with a similar idea, taking advantage of the modder LagoLunatic’s DSVania Editor to combine the two.
The readme.txt gives describes the mode as follows.
“An alternate timeline where Dracula’s force has taken over the future of mankind, but wait…CONTRA is still alive! Contra has built their first ever time machine to go back to the past and is ready for some Dracula’s ass-kicking duty!”
You can download the mod from the RDHN page, and will then need to apply one of the six patches for the characters to the game to get it to work on a DS emulator.