December 20, 2015 Patch

{{Patch layout
 * sort = 2015-12-20
 * source = http://store.steampowered.com/news/19780/
 * source-title = Dota 2 Update - December 20th, 2015
 * before = 2015-12-18
 * after = 2015-12-21
 * notes =

6.86b
}}
 * Enabled, , , and  in Captain's Mode
 * Rune icon Arcane.png Arcane Rune mana reduction reduced from 50 to 40%
 * duration increased from 4 to 5 seconds
 * intelligence steal increased from 0/1/2/3 to 1/2/3/4
 * cooldown rescaled from 20/17/14/11 to 22/18/14/10
 * backstab damage multiplier increased from 0.4/0.6/0.8/1.0 to 0.5/0.75/1.0/1.25
 * now only affects heroes
 * AoE increased from 450 to 475
 * cooldown rescaled from 90/80/70 to 70
 * AoE increased from 650 to 725
 * slow rescaled from 4/6/8/10 to 7/8/9/10%
 * duration rescaled from 6/7/8/9 to 5.5/7/8.5/10 seconds
 * damage rescaled from 175/275/375/475 to 180/270/360/450