All DoT spells deal their damage every half second. Meaning, it would appear that you are doing half the damage, but if you look at it PER SECOND, instead of per tick, you are doing the correct damage. Crowstorm and Drain are both DoT spells.

Why would I even open new tread If I wouldn't have exactly correct stats. Why would I waste my own time and eventually yours by trying to lie to anyone checking this thread?

What im trying to do Is understand the mathematics behind his spells and attacks.

A link with explanation of MP and what lowering MR does would be very helpful, anything that will bring be reasonable answer

Now that's an answer I was looking for. Thx mate =) you are helpful indeed. Where can I further check if champions have DoT spells?

my post got overlooked i spent too long typing it

no I've read your post also =) thank you for your time typing explanation =)

Don't be a smartass. It wouldn't be the first or even the 1000th time someone has posted something sensationalist without having correct information. Also if you bother to read my entire post, you'll see the answer was in there, and was confirmed by others afterwords.

On Topic:
Damage Reduction = Total Magic Resistance / (100 + Total Magic Resistance)

Magic penetration allows spells to bypass magic resistance without going negative. Magic reduction can go negative and is applied before penetration. It will also lower their resistance for everything that hits them(including your allies abilities)

So.. someone has 30 MR you have 20 MP then they have 10 MR left and then you do more dmg with your spells then before ( but not over max limit written next to spell ).

with 30 MR they resist 30 / 30 + 100 of incoming spell dmg and then they resist less dmg
10/ 10 +100 . and If you lower MR with abyss scepter you lower it for the number written in item discription exactly. Hope I got it right. thx for your help

Well I have a question here. I've always been curious. Being as magic resist seems to be straight numbers, wouldn't items like void staff and the mastery for magic pen actually be less than what people consider them to do? They are percents if I am correct. IE: The offensive mastery would only decrease it by .15, instead of 15 which some people seem to believe?

Yes they do. Drain's Damage is showd every 0.5 second interval so you will se the damage for half of what it sais on the tooltip since the tooltip is based on full seconds. Not sure about His ulti though. Azurath just stfu he is making a valid statement. Given 30 Mr on enemy champion and applied certain (whatever amount you want) of magic pen and/or magic resist reduction he should do more damage than without it. You should be careful with the maths though since a Tristana with 30 base MR is already down to 14(i think) from fiddle's passive. And you have no way of testing it without fiddle's passive since it applies as soon as you get within champion range. Try using higher numberse like 100 MR on the enemy champion.