Is it possible to include a magic damage type thornmail? Ryze throws for 600 and gets hit with 180

This.

WIOT PEEEZ

Well except for the fact that it's going to take Tryndamere more than twice as long to kill you, and he's killing himself extremely fast while doing it. Thornmail's actually very effective against him.

Oh, you were going to ult and see if that lets you survive? Glad I always run with Exhaust or Ignite.
No. NO no no no no NO NO NO no NO no no NO NO NO we are NOT building a magic Thornmail.

Not only would it negate the existence of burst casters, but due to how spells and abilities are coded in the game, it would have a profoundly dangerous effect against non-mages who use spells. There's also the coding loop where item damage=spell damage, meaning two magic thornmails would reflect damage back and forth between each other until you get down below 0.001 damage return. And let's not forget that someone could grab both of these thornmails and be an invincible juggernaut.

Quotes a 2 year old post.

Fails to realise it's a 2 year old post.

Still get's his information wrong.

Wow Ex, you've really managed to fail on this one. Tryndamere still loves Thornmail, because it allows him to reduce his own life in order to deal more damage. If the enemy team is avoiding focusing him down (in an attempt to minimize his contribution because his allies are bigger priorities), then he can manipulate his DPS against a target with Thornmail.

Yup, I failed to notice the age of the post. Good catch.

However, do you think Tryndamere really likes losing his HP for a measly 35 AD steroid that is going to get more than half of it cancelled and then 1/3 of it returned to him?

Even just 161 Armor (61.7% resistance) means that his AD steroid increases his damage by 13 per hit, 26-34 per crit, meanwhile the damage return is increased by 11-27.

Minuscule increase overall.

An enemy having Thornmail means they don't have Omen or Heart. This is why Tryndamere loves the item. If they DO have Thornmail AND Omen or Heart, they've spent a huge amount of gold on countering Tryndamere, and he can dedicate his teamfight presence to the other 4 members of that team. Especially if they have Omen; an enemy who has Omen is very dangerous for Tryndamere, but if that enemy is also one he has to kill early then it makes his life miserable (like a ranged carry or Xin Zhao/other burst AD). If they have Thornmail AND Omen, then he simply doesn't care about that target; they've used up 40% of their item slots and 5000+ gold to counter him, and he can just target someone else.

And if, by chance, they decide on Thornmail and some HP/offense item instead, f'rexample Rylai's/Mallet? Suddenly they're guaranteed to outlast Tryndamere, because their physical EHP is definitely higher than his magic EHP; the damage from Thornmail alone will deal a ton of damage, let alone the champion's innate skills/DPS. Now Tryndamere needs to spend money on MR so he doesn't murder himself targeting a mage who deviated slightly from their core build for a 2k gold Armor item.

I'm not debating that Heart or Omen aren't better, but that Thornmail is a solid item.

Specifically, it's good on mages and/or melees, because they're less likely to be able to afford Omen in their build; Frozen Heart is another matter regarding some mages, though it's far more likely to be something the team's tank builds.

As an anti attack item, Warden's Mail is better than Thornmail. If the defensive slow triggers, it renders Tryndamere effectively useless for the duration UNLESS he has a Frozen Mallet. If Tryndamere needs to buy Frozen Mallet, he's effectively frozen his build until he's able to farm to make up the difference. This deterrent is far more effective than the damage reduction from Thornmail. The return damage means much less to Tryndamere than any other auto attacking champion, because he thrives on being low life. Mundo thrives on low heath, but not so low he's near death; Olaf skirts the edge, barely hanging on during his ultimate. Tryndamere literally wants to be 1 health as long as he possibly can. Thornmail allows him to regulate that himself.

Thornmail is a bad item because Randuin's Omen and Frozen Heart exist. What Thornmail does is easily countered or ignored by anyone it's designed to counter. The only scenario it's useful is an edge in a carry versus carry fight; other scenarios, other items would be better suited. Randuin's Omen comes with health and a slow, making it at least somewhat useful against mages. Frozen Heart comes with an attack speed slow and 20% CDR, making it useful for anyone and passively counters auto attacking champions.

Yes. Thornmail is, by comparison to Heart/Randuin's (and yes even Warden), noticeably less useful.

Particularly if your opponents are really good at focusing the same target all at once.

It's also true that Tryndamere just barely benefits from Thornmail, never mind the massive negative to his damage that it causes just to get that +35 AD which he could just as easily get from a wandering Malzahar.

I'm just saying, Thornmail is not a bad item. It's cheap, it deals extra damage, and it gets close to doubling your EHP. It allows someone like a carry or pure damage mage to quickly deviate from their build for some defense+offense.