Basically play as Richter Belmont in SotN, but no running, dashing, whip-swinging or uppercut unless needed in situations such the need to progress the game for further areas. And that pointless one-room gaps in metroidvanias between Areas, go ahead. Dash Jump that. In Areas such as Clock Tower, you can't simply walk there without the ledges falling down. You can explore areas for sub weapons by using super jump for example the Clockroom in Marble Gallery. The easy mode for this is, you can collect Life Ups and the Hard Mode is no Life Ups. Now in the Challange, you are NOT allowed to use any bonus SotN abilities, but sub weapons such as Agunea and Vibhuti don't count here. There are some instances that Legion is not meant for RoB play style unless you are trying to hydro storm it, legion is too high for you to jump and whip I think. If its impossible to beat it with RoB style, then finish it with your SotN abilities but this is only acceptable if impossible, not for difficulty or else you've lost this challenge. It's pretty fun. At least for me. So far I've defeated the Giant Bat in the reverse castle.