Rek Sai is a champion that has found a lot of success in past season. Notably in 2015 and 2016, she was arguably the best jungler at that time. Combine with her toolkit, and huge knockup potential, along with the fact that she could be EXTREMELY tanky, she was a threat to be reckoned with.

But with recent patches, Riot seems to be pushing her away from the tank style to more of an assassin type jungler. Her W got nerfed so instead of having the potential to knock up an entire team, you can only knock up 1 target, as well as her ult getting changed. With all these reworks she moves towards being more offensive.

While yes you can dominate the early game, but unless you keep consistently snowballing, you become much more useless in the late game. If you build for more of a tanker build, you can still be very relevant throughout all points of the game

As a tank, you aren't too strong in the early game. Once you get level 3, you can still get good knock ups, but you become a much better threat after level 5.

With the tunnels, you have a lot of good mobility. You can go through a lot of walls that most junglers can't get over, which lets you get a lot of good ganks. Tunnel also goes a good amount of distance. The tunnels also let you escape a lot of situations.

When in team fights, be careful who you knock up. Because if you knock up the wrong target, you are in the middle of the team and could die very easily. Try to aim for one of the carries to minimize the enemy team damage output.

In the mid and late game, assume you aren't behind, you become such a powerful tank. You have a lot of health and resistances, meaning you shouldn't be afraid to go for engages.

I feel like the items are mostly self-explanatory. There isn't really much to discuss, except if you are losing the early game. If that's the case, give up Black Cleaver and Titanic Hyrda, and go straight to tank.

GA should almost always be bought, whether behind or ahead, it allows you to go for more risky plays, as well as a lot more survivability.

The aftershock runes are pretty standard if you are looking at it as a tank.
- Bone Plating is really good, especially in team fights
- Overgrowth helps a lot, especially as the game the game goes on you can get 100+ additional health minimum.

The inspiration rune may look like a surprise to most people. The reasoning for magical footwork actually makes a lot of sense. If you are active enough throughout the map, you can actually get boots early, which helps you save gold to buy other needed items. Cosmic Insight is also just a nice little touch. Inspiration also give you more additional health. Another good option over Cosmic Insight is Stopwatch.