Tryndemere is a very strong hero, and is never on mid lane, i wonder why since every hero on mid lane is really weak early game trynd can crit them down in just a matter of hits and can roam around around from mid and get that critical farm/kills to build a early infinity edge

The crit runes and armor pen runes are almost essential for a earlt kill, becouse it pretty much almost casters mid they are around 30 armor and with the armor pen your crit will take them down much quicker
And for the crit runes, it's trynd the crit hero

In The masteries tree i've taken all of the crit branches to improve trynd performence in early
/mid game and also in late game

The item setup that i recomend you to build have i been experimenting with under my time with mid trynd and come up with that this is the best build, start with a beserkers claw and right after build a avarich blade, but if you get first blood and get good farm go right for executioners calling, keep in mind excecutioners calling is an awesome item if you happen to face volibear cuz he's passive will not heal as much, other than that just keep the item setup

In the middle part of the game you should farm the hole time to get that cs up, when the minions is on they're part of the map, go jungle right away, and if there is a big creep way, tell your team to leave it to you so you get that extra income

Even though you're ultimate undying rage you should never tank a game, they will focus you down and you're ult will be wasted instead go in behind them and take the easy targets first that you can 2 hit if you have had a really good farm