Originally Posted by Sasho1233
This part is uncodeable. Or at least it will not work properly, as we can't differentiate physical attacks from nukes. You'll end up with Backtrack, and we already have that skill.
I didn't know about this Warcraft III engine limitation.
BUT, it can be coded in a very easy way.
Make Blur an ability based on damage block.
Level 1 - 20% chance to block 99999999 damage.
Level 2 - 25% chance to block 99999999 damage.
Level 3 - 30% chance to block 99999999 damage.
Level 4 - 35% chance to block 99999999 damage.
She takes 1 damage when this triggers, but it's a negligible side effect. Works well with Vanguard or Poor Man's Shield if you skill Blur after you buy one of these items (source: http://www.playdota.com/mechanics/Item_Passive_Stacking
Even if it would make Poor Man's Shield and Vanguard rather tabu items for Mortred, I think the advantage of having Butterfly greatly surpasses the benefit of an extra damage block.