Great work here! The RNG never felt too punshing, solid game that kept me engaged until I died. Good difficulty curve and the learning was fairly easy. I got to level 30 first go! The following feedback is made knowing what you have feels like a complete package, and you probably didn't have enough time to add anything else :)
* A third tier for every item combo would be appreciated. I had several instances of 3 two-tier items and was sad they didn't merge. I think a 4th tier would be a bit overkill
* Adding deck kickers that let me clear some fluff would be great. Then I can keep getting stronger and get rid of the chaff
* Some mutation/"mergability" of non-compatible items would be extra solid, adding an entire extra dimension of choice to the player. i.e. merging a potion with a bone to heal 1 / damage 1?
* More visual effects / sounds would go a long way
Solid entry, good work!