Conversion makes me think of Rustler, except with a different mechanic and theme. I like it.
I don't think you need to raise the cost by 1 for the upgrade though - considering that this "produces" less than Rustler overall (Rustler require 1
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-> 2
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. This requires 1
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+ 1 card -> 2
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at least), you could possibly lower the cost to 3 | 2 and make the unupped generate
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as well, unless there'd some gamebreaker deck that I didn't think of.