Building ap to make mei an off tank nightmare to kill. This build the synergy between wall, pillar, and sustain. I have gotten over 3k self heal in a single round with this build. I prefer it coulder, since coulder turns a defense ability into offensive.
Item purchase order
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Round 1
[Ice Wall] spawns a mini [Blizzard] that slows enemies.
1,000 
1,000 
1,000 I like weapon speed and weapon lifesteal for the first round to help you stay up and alive, but it's up to you. I would suggest getting power playback right off the bat. The wall dmg is long and thus ignoreable, but that just means free ult charge.
Round 2
1,000 1,000 
1,000 
3,750 
6,000 
4,000 
After you spend your Ultimate Charge, gain 25 Armor and 10% Ability Power for the rest of the round.
1,000 If you can get 15k to 16k in the first round you can get icy veins early, but at this point it isn't really worth it. You can more than double the ap with blues and greens. If you can get 30 ap with icy veins get icy veins, otherwise just go for 50% ap with blues. But that's just in an ideal case, forego nano cola if you didn't do well and get survival items. The green 1.5k ones
Round 3
Increase your max health by 50% of your ability power.
After you spend your Ultimate Charge, gain 25 Armor and 10% Ability Power for the rest of the round.
1,000 
[Blizzard] deals 100% increased base damage.
10,000 I very much recommend permafrost this round, and icy veins for an item. Permafrost will give you around 430hp this round. Having the larger hp helps you stand beside your tank, and gives you a bit more wiggle room for cycling you abilities. You could grab Snowball flight here instead for extra dmg, but picking it here makes you much more of a glass canon.
Round 4
6,000 
14,000 If you just so happen to be the goat and have more than 30k lying around at the end of the 3rd round then keep nano cola and stack as much ap as you can. It's that easy. This round regardless I think you should get champions kit, you should have enough for it icy veins and ap lifesteal power. If you don't have enough then get iridescent iris instead of champions kit, that should let you get the greens. But the basic idea is still just building ap, for bigger hp bar, more dmg with wall.
Round 5
Jumping while mid-air creates a large [Ice Wall] pillar under you. (12s Cooldown).
1,000 
After spending your Ultimate Charge, gain 100 Overhealth for 3s.
11,000 Making it to round 5 makes you very cockroach like. It you are having trouble surviving phantasmic Flux instead of iridescent iris is a good choice. The cooldown reduction isn't as good on this build since snowball flight isn't effected by it, but it is still nice for wall and block.
Round 6
1,000 3,750 6,000 
While at full Life, Lifesteal grants up to 100 Overhealth.
10,000 This is my usual end state, as it is hard to farm enough cash for everything, but this will make you incredibly tanky will scary dmg on wall and pillar. With all the self heal you can stay in a fight for quite awhile and build ult very quickly.
Round 7
While within [Blizzard], heal 5% of your life every 1s.
6,000 4,000 
Ability Power is increased by 5% per each spawned Ice Pillars.
10,000 
Restore 3% of your Life every 1s.
10,000 This is the ideal build but it almost never happens. The 6 purples really add up. There are two you can lose at this point if can't afford all of this. And that's Phantasmic Flux and Sturdy Snowfort. With blizznado as add survivability Flux is less useful and snowfort is good, but not necess at this point. Nano cola and energized bracers are just fine replacements.
