Talk:The Black Cleaver/@comment-12727893-20130922080323/@comment-18521310-20130922083501

Wikia decided to eat my previous comment, so let's try this again...

and absolutely stack. Specifically:
 * Stacks from BC reduce enemy armor total.
 * Percent penetration from LW applies.
 * Flat penetration from BC applies.

So, as an example, let's say you're fighting a champion with 400 armor (Perhaps a ) and have applied all five stacks from BC. Let's see what his armor looks like for your next attack:
 * First, BC removes 25% of his armor. Armor = 300.
 * Then, LW ignores 35% of that. Effective armor = 195.
 * Finally, BC ignores 10 flat. Effective armor = 185.

To compare:
 * Effective armor with neither: 400 (80% damage reduction)
 * Effective armor with just BC: 290 (74.4% damage reduction)
 * Effective armor with just LW: 260 (72.2% damage reduction)
 * Effective armor with both items: 185 (64.9% damage reduction)

So, as you can see, having both provides more than a 7% more damage than just LW, and almost a 10% more than just BC.