Talk:Kayn/@comment-37806371-20190228153012/@comment-17903049-20190317051535

Magic pen would increase the passive damage dealt, so you can get it if you think all the other boots aren't worth it. Yes, the main source of damage is physical, and yes, you are gonna lose the passive after 3 seconds of fighting (which no fight should require you to fight more than 3 seconds other than ending the game or you are misplaced) making the boots mostly worthless.

As for the other boots: Berserk, Swiftness (E cancels slows), and Ionian are (mostly) useless; Mercs are nice but if you get CC'ed you lose E and speed, so any hard CC, regardless of length, is bad, while E itself cancels all slows; and ninja is good in teamfights, but again, you aren't gonna be in any.

As such, you are left with 2 options: Sorc or Mobi. If you need the mobility, go mobility. If you don't, go Sorcs.