you can get + and - items that you can equip to your monster to control that stuff. it's the same as the egg dude in DWM1.
man, just talking about this makes me want to bust it open again. I have a weird nostalgia for DWM which is weird because I played it for the first time in like 2005.
anyway - Joker made some good changes. 100 monsters is so much better than 20. breeding itself was kinda cool. add that stuff to DWM's charm and more fulfilling content and you could have something great.
you just have to not go overboard and implement the ability system or the level cap stuff.
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xyzzy