How to defeat the Giant Sapling in Clair Obscur: Expedition 33
The Clair Obscur: Expedition 33 continent world map is filled with secret bosses, locations, and areas which you'll never come across if you focus solely on the main story. One of those areas is the Crushing Cavern, which houses the Giant Sapling, a tough boss that challenges you to race against the clock as crushing rock walls close in from either side.
If you haven’t found the Crushing Cavern yet, it's located just west of the Stone Wave Cliffs and is only accessible from act two onwards, once Esquie unlocks the ability to swim.
How to defeat the Giant Sapling in Clair Obscur: Expedition 33
First off, it's important to note that the Giant Sapling boss doesn't have a gimmick. Fighting it for the first time you might have assumed that there's way to stop the stone walls closing in to squish you—as far as I can tell, there's isn't. The Giant Sapling boss is a timed damage check, plain and simple, as you try to obliterate it before the walls snuff you out.
While you can simply come back later when you're powerful and annihilate it without too much trouble, if you want to defeat it early for the reward, I suggest using a combination of damage buffs and high-powered skills that deal Break damage. You'll also want to equip damage and critical hit boosting pictos and lumina to do as much damage to it as possible.
Breaking the Giant Sapling is key here, since it'll give you an extra turn to throw some damage at it without the walls closing in, but it'll recover shortly after and continue closing the walls. One strategy—similar to what I used to deal 9,999 damage to Ono-Puncho—is to utilise Maelle’s Percée skill in Virtuoso Stance and boost it by marking the boss with the Marking Shots picto you find in the Flying Waters.
Lune is also a capable damage dealer once you unlock Mayhem and consume four stains when using it. That said, if you're struggling with the Giant Sapling, I'd suggest that you return a little later in act two. This is what I did and I completely annihilated the boss in a couple of turns using Lune's Mayhem with the Confident Fighter and Immaculate pictos for 60% increased damage.
Once you defeat it, you'll get a Polished Chroma Catalyst and the Solidifying picto, which gives the party member +2 shields when their health falls below 50%, once per battle. You can also find a Colour of Lumina and the Expedition 45 log entry back up above where you fell through the floor. That's everything in the Crushing Cavern!