Elden Ring: Shadow of the Erdtree has a new levelling system to help you take on all the seriously strong bosses in the DLC: Scadutree Fragments (which are apparently pronounced Shadowtree Fragments). The only catch is that, along your journey to get these new fragments, you'll have to go up against some tough opponents.
Unless you're this player who posted a map to Reddit: "You can get Scadutree Blessing level 12 without killing any bosses."
You can get Scadutree Blessing level 12 without killing any bosses from r/Eldenring
If you follow the route given exactly, then you shouldn't have to walk through a single fog gate, leaving you to level up your Scadutree Blessing in peace. Another player even points out that it could even be possible to get to "14 or 17 before any remembrance bosses." So if you're careful enough, you may be able to get ridiculously strong without a single scratch on your tarnished.
Still, if you're up for a scrap, killing the Golden Hippo and Commander Gaius will mean you can get every Scadutree Fragment in the game apart from the ones found in Enir-ilim.
While this could be a useful strategy for those who just want to bolt through the DLC, dodging bosses may mean that you'll miss out on some of the story. However, as a player points out: "I don't think you can 'ruin' the quests, you just miss some steps … After beating Relanna, I broke the seal fairly quickly before even finding Thollier, and I still finished all quest lines. All I missed out on was lore and an incantation."
FromSoftware has stressed time and time again how important Scadutree Fragments are. In response to an outcry from players saying the DLC is too difficult, the publisher Bandai Namco simply reminded everyone: "This is a suggestion to level up your Scadutree Blessing." These are pretty much the only things that'll protect you when facing up against Shadow of the Erdtree's bosses, which are a new tier of suffering.
FromSoftware even buffed the Scadutree Fragments in a recent patch. This means the first 10 levels will give you a bigger boost, and after this, the progression will feel more gradual. So exploring the DLC to find every Scadutree Fragment possible will certainly pay off, at least for a little while.