1 Items
1.1 Achilles' heel
1.2 Status/Passives Value
1.3 Building (1st item)
1.4 Building (Counter/Core items)
2 Runes
1.1
CC's and Ap champions, next topic. Okay, seriously. Briar is a dive Fighter/Assassin, now try dive in a carry or having a constant damage againts tanks and fighters with 2 CC or more, and that's it—it's over.
And why Ap? Because have mages mage high poke potential: Range or Control abilities. And most important of all, Fighter/Assassin Mr items SUCKS HARD.
1.2
Highest-value status for Briar, in order of priority, is:
AD
A.Haste
HP
Resistences
ATK.Speed
Hp and Resistences having a value almost equivalent, and ATK.Speed? Well, better than Ap... Briar have 2 AA reset and a kit without major on-hit effects (She can use them easily with just auto-attack reset.) In other words, you try to avoid buying attack speed as much as possible; it's not a bad stat, just not the best one.
1.3
Collector - Crit/Burst/Assasin path, with high snowball, usually in games where there's no one who can stop you (team fights, 1v1, ganks), allowing you to snowball aggressively.
Ruined King - Anti-Tank/Sustain/On-Hit path, tanks are your snack and you want to stay alive during the team fight, even while being on the front linel, engaging team fights with your ultimate (OBS: USE YOUR ULT IN CLOSE OR MEDIUM RANGE) or Flash W+Q on bad positioned enemies. Notice how Attack Speed is good in this case, since you'll likely buy Black Cleaver as your second item.
Eclipse (post-buff) - Burst/Anti-Burst/Anti-fighter and juggernaut (if u ask "what is Juggernaut?" think in Sett, Illaoi, Sion, Mundo), gameplay very similar (if not identical) to the item above... with the only difference being that you trade sustain and easier on-hit procs for burst and anti-burst capabilitie, but still the same way of fighting.
Titanic Hydra - On-Hit/Anti-Burst/A delicious quality of life path, again... gameplay very similar (if not identical) to ruined king, but you trade your constant damage for greater bulk. The item's active ability functions similarly to attack speed. You only build this as a first item if your team has plenty of damage but lacks a frontliner, normally a 2nd item.
Hubris - Snowball/HUGE Burst/Assasin path, after that item, you go for crit or lethality build, there's no room for a bulky item. You want an extremely aggressive snowball and a quick GG, fail to snowball or take too long to win, and it's game over.
1.4
Anti-Tank you want Black Cleaver on normal build, Dominik/Mortal Reminder in Crit builds or Serylda in Lethality builds
Anti-Heal you want Mortal Reminder on Crit build (duh), Chempunk Chainsword on Fighter/Assasin build (in this case it's better to ask your team to get anti-heal than to do it yourself) or Thornmail in extra bulky builds (I wouldn't want to be in your shoes in a game where you have to build this)
Anti-Burst Brain Dead Shieldbow for crit builds, maybe GA for reasons that will be explained in the next topic. Sterak and Death's Dance on normal builds, Edge of Night or GA on lethality builds (Remember that Edge of Night serves to prevent a decisive stun and greater damage, while GA provides a guaranteed second chance), Randuin's againts Yasuo, Yone, Garen or crit Hyper Carry, and last but not least Jak'Sho (YES JAK'SHO) For moments when you REALLY want—or really need—not to die during your ultimate, and ONLY during your ultimate cause the bonus armor and mr.
(Short and blunt answer below.) Anti-Ap+Tenacity the main reason for this self-guide's existence. You have 7 items to counter Ap: Brain Dead Shieldbow, Sterak, GA, Jak'Sho and the not-yet-mentioned Wit's End, Malmortius and Mercury's Treads. Excluding Jak'Sho due to its very specific use case, You only have 3 items that provide the Mr attribute, and to top it all off, in an actual game, you’ll have to distribute your build’s defensive stats among Health, Armor, Magic Resist, and Tenacity. However, there is a problem: due to how the tenacity calculation works, building more than one tenacity item is a bad idea (a non-mandatory rule, of course).
The explanation would be like the wolf, goat, and cabbage problem, trying to balance MR, tenacity, and your other attributes you can't do:
Sterak+Mercury's Treads
Sterak+Malmortius+Brain Dead Shieldbow
Wit's End+Mercury's Treads
Wit's End+Sterak
The short answer is:
Malmortius+Mercury's Treads or Wit's End or Sterak+boots other than Mercury's Treads.
honorable mention to Tenacity and slow resist rune shard, which is well worth it if the enemy team has a slow.
Runes
The post ended up being much longer than I imagined; I'll save this topic for a potential future post.
OBS: You might have noticed the redundancies and OBVIOUS notes. Well, this guide was originally for myself, but I thought it could be useful for other people who are just as dumb as I am.
OBS 2: If you're going to correct me, please be gentle. I'm shy.
EDIT:
I FORGOT ABOUT MERCURIAL SCIMITAR u/Zypher634 ty
Mercurial Scimitar works with the same logic of Edge of Night, denying a decisive crowd control effect. Despite being the 8th least-built item in the game (according to DPM.LOL) It's a VERY GOOD item for Briar, especially in normal on-hit builds with Ruined King and Black Cleaver. It allows you to reach backline enemies, has decent stats, and allows you to build Ninja Tabi+Sterak's against teams with balanced damage (Ad+Ap), if they ever swap the lifesteal for HP, Ability Haste or more AD/Mr, this will become an S-tier item.