What is the point of even having Thornmail in the game? Armor is nice, but its not health. Reflecting aa damage? Thats cool too, but a vamp scepter alone counters the damage it deals back. Short of the enemy team having all adcs with no lifesteal there isnt really a use i can figure out atm. Am I missing something?

I don't think thornmail is bad,
It's more of a problem with Radium's and Glacial shroud providing pretty much the same protection (if not more) with better additional stats and supportive effects.

I think that's what Ballz is saying. The only thing making is special from those other items is it's passive, which is pretty much useless at this point. The only person I build it on still (and not even always) is Rammus... who kind of needs an upgrade as well.

Thornmail has a solid effect when your opponents are based on physical damage and primarily use basic attacks.

It's a niche item, but it's actually fantastic for countering Lifesteal stacking and handling Xin Zhao.

How does it counter lifesteal? Lifesteal counters the thornmail passive. If your healing back the same amount of damage your taking from the passive. Its not really a passive id like to have. Minimal amounts of Magic resist essentially cancel the damage it does. Its a niche item for 1 champion. This needs reworked or deleted with the current game there is no reason for this item to exist. Also even if a tank got a thornmail. As an adc i will just laugh and melt his team while i ignore him. Why would a tank want an item that makes u not want to attack him??? Yet another reason this item needs removed.

No, a vampiric scepter doesn't. Thornmail reflects 30% damage back and vampiric scepter only restores 10% health. Beyond that life steal is based off of the damage you deal (which is subject to armor reductions - which should be around 200 with thornmail on base armor values). Thornmail's reflected damage on the other hand is applied before the damage you take is mitigated by anything - which includes armor or blinds. Of course it's magic damage, but you're not likely to have much in the way of magic resistance if you're building the AD to support life steal.

But to get life steal to the point were you stop taking damage from striking thornmail, for 30% life steal to counter 30% damage reflection you need to have your effective magic resistance (after enemy magic penetrations) equal to you're targets effective armor (after your armor penetrations).

Here's the thing you're mistaken on.

Thornmail's damage return is pre-mitigation, while Lifesteal is post-mitigation. This means that Armor reduces Lifesteal directly, but does not affect Thornmail's damage return (it IS affected by enemy MR).

So, if you have JUST Thornmail, your armor at level 18 is going to be 161-190, which is 61.7-65.5% damage reduction. You're taking less than 40% of their AD per hit if they have no Armor Penetration.

Meanwhile, base MR being 30-52.5, Thornmail is returning 19.7-23.1% of their AD to them.

Just based on Thornmail vs Lifesteal, the attacker needs 51-67% Lifesteal to NEGATE Thornmail. It takes a combination of Lifesteal, Magic Resist and Armor Penetration to make Thornmail useless.

Besides you're not supposed to just stand there and let them attack you, if you attack them too. it'is like you are buffing your damage output. Also, if you have ignite, then it is even more powerful.

What if Thornmail dealt the return damage as Pure damage?

why doesnt it return spell dmg? even physical spells, thornmail is useless on enemy pantheon with bc, spaming his q and e and u just lose armor and pantheon takes no damage return. so it is useless against ad casters and only effective on ad carries?