While a large part of Returnal’s gameplay is about dodging incoming damage, in bullet hell games you often have little choice but to eat some shots. If you really want to be able to survive the late game in Returnal, you will need to increase your maximum health.
In Returnal, this is known as suit integrity, and you can increase it over the course of the game to become tankier, and able to take much more damage.
The Resin Method
To increase your suit integrity, you will need to find resin. Resin will be marked on the minimap by green cross icons. Pickups marked with this items have a chance to be either healing items called Silphium, or the Resin items that you need to increase your suit integrity.
On the bottom left of the screen you will notice three small dots beside your health bar. These will be filled in by the resin that you pick up, and when you fill in all three, you will get a new chunk of health added to your overall health bar. A small piece of resin will fill in one dot, while a big piece of resin will fill in two.
When it gets interesting is that if you already have full health, and silphium you pick up will count as a resin instead. This means you will need to choose between leaving heals on the ground that you may need later, or using them as resin instead.
Throughout the game you can find different parasites that will give you some kind of benefit, but you need to accept a debuff as well. These can increase your suit integrity, but it is impossible to farm specific ones that give the exact bonus you want.
You can purchase a 25% health increase at any Fabricator for 350 Obolites. Obolites are the small golden energy shards that you can collect from defeated enemies.
Remember, health buffs earned over the course of a run are lost when you die, and you always begin each run with your default health pool.