Iwer Sonsch | How to win with RIVEN on LEGENDARY (Lab of Legends, Runeterra) - 44:33 Former Speedrun WR @iwersonsch5131 | Uploaded June 2021 | Updated October 2024, 2 hours ago.
In this video, I complete the Lab of Legends campaign with Riven on Legendary difficulty. To do this, I start with Lil' Buddies, and find Tahm Kench and Evolution. Items were less important.
Tahm Kench most definitely isn't the best second champion, but Evolution may well be the best second power you could find.

Even without Evolution and Duelist, however, I believe that Lil' Buddies gives Riven all of the necessary board control to defeat Von Yipp's swarm at the Foundry, the hardest stage in the game.

It should do this more reliably than Sorcery (which has to hope for Culling Strike in the opening hand), and far more reliably than going for synergy immediately with Evolution or Domination, or generic power with Spellslinger or Manaflow.

On top of that, Lil' Buddies provides notable support at every level in the campaign except for Scars (which Riven already counters thanks to her abundant damage buffs), something that Sorcery and other powers struggle to do. It also opens up more synergy points for the second power than just Evolution, including Rush Them Down, Sharing Is Caring, and Yipp's Genius.

I played one attempt comfortably past Thresh before realizing that my recording settings were off, then I reset and completed this run on my second attempt. I never failed with this strategy.