When you buy a rageblade you get (at lvl 18) 15% Armor and Magic pen. However when buying another % penetration item (for example a Last Whisper, this value of 15% gets overwritten to 10%.
Steps to reproduce:
1. Buy a Rageblade (observe how you have the correct amount of % pen)
2. Buy any other % pen item
3. You now have the incorrect penetration value.
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