my packdefinition file is:
<packdefinitions version="1.0">
<pack>
<packtitle>Booster Pack</packtitle>
<packimage>samplebooster</packimage>
<packformat>Normal</packformat>
<packkind>booster</packkind>
<packcommoncrit><field>Set</field><eval>IS</eval><data>Alpha</data></packcommoncrit>
<chance>
<prob>30</prob>
<kind><qty>1</qty><crit><field>Type</field><eval>IS</eval><data>Champion</data></crit></kind>
<kind><qty>4</qty><crit><field>Type</field><eval>IS</eval><data>Creature</data></crit></kind>
<kind><qty>4</qty><crit><field>Type</field><eval>IS</eval><data>Magic</data></crit></kind>
<kind><qty>2</qty><crit><field>Type</field><eval>IS</eval><data>Resource</data></crit></kind>
<kind><qty>2</qty><crit><field>Type</field><eval>IS</eval><data>Attachment</data></crit></kind>
<kind><qty>2</qty><crit><field>Type</field><eval>IS</eval><data>Field</data></crit></kind>
</chance>
<chance>
<prob>30</prob>
<kind><qty>1</qty><crit><field>Type</field><eval>IS</eval><data>Champion</data></crit></kind>
<kind><qty>4</qty><crit><field>Type</field><eval>IS</eval><data>Creature</data></crit></kind>
<kind><qty>3</qty><crit><field>Type</field><eval>IS</eval><data>Magic</data></crit></kind>
<kind><qty>3</qty><crit><field>Type</field><eval>IS</eval><data>Resource</data></crit></kind>
<kind><qty>2</qty><crit><field>Type</field><eval>IS</eval><data>Attachment</data></crit></kind>
<kind><qty>2</qty><crit><field>Type</field><eval>IS</eval><data>Field</data></crit></kind>
</chance>
<chance>
<prob>30</prob>
<kind><qty>1</qty><crit><field>Type</field><eval>IS</eval><data>Champion</data></crit></kind>
<kind><qty>5</qty><crit><field>Type</field><eval>IS</eval><data>Creature</data></crit></kind>
<kind><qty>3</qty><crit><field>Type</field><eval>IS</eval><data>Magic</data></crit></kind>
<kind><qty>3</qty><crit><field>Type</field><eval>IS</eval><data>Resource</data></crit></kind>
<kind><qty>1</qty><crit><field>Type</field><eval>IS</eval><data>Attachment</data></crit></kind>
<kind><qty>2</qty><crit><field>Type</field><eval>IS</eval><data>Field</data></crit></kind>
</chance>
<chance>
<prob>10</prob>
<kind><qty>1</qty><crit><field>Type</field><eval>IS</eval><data>Champion</data></crit></kind>
<kind><qty>5</qty><crit><field>Type</field><eval>IS</eval><data>Creature</data></crit></kind>
<kind><qty>2</qty><crit><field>Type</field><eval>IS</eval><data>Magic</data></crit></kind>
<kind><qty>3</qty><crit><field>Type</field><eval>IS</eval><data>Resource</data></crit></kind>
<kind><qty>2</qty><crit><field>Type</field><eval>IS</eval><data>Attachment</data></crit></kind>
<kind><qty>2</qty><crit><field>Type</field><eval>IS</eval><data>Field</data></crit></kind>
</chance>
</pack>
</packdefinitions>
but somehow cards from a different set is keep showing up.
the second set is called UnChart it's made from my 12 YO sis's Drawing so it's kinda funny looking(my Alpha is not much better though)
but the balance is not the same on the two sets as one have been heavily edited and the other is under construction so it is a problem when i playtest with "Booster Pack" and get something like "Radioactive Foot" in it.
I can't find anything wrong in the packdefinition that you posted. The problem must be elsewhere.
If you upload your plugin - sans the images - I can take a look at it.