Protecting your party members will make your life easier. Urtuk: Desolation. Unfortunately, many of them are required to take significant damage, and some of them may fall in battle. When they do, you need to make sure you give them the right treatment to get them to recover. You can also aid them in combat by giving them specific abilities and mutations to aid in recovering health during combat.
When you complete an encounter and bring down party members, they suffer an injury. You have to go to the party menu on the right side of your screen and give them some medicine if you have it. Highlight the character you want to deliver the drug to and apply it. Depending on the injury, the character needs a few days of rest before they are no longer injured. If a character descends into combat while healing, they die and you do not return.
During combat, your characters should exercise caution. Most of the spells you use will increase their chances of receiving life steal when you hit an enemy. You want to strategically formulate which characters can use skills to make your party members appear alive and which Mutators they have active to further enhance it. Potentially, a character could unlock a trait to have life steal attacks restore them to more health when attacking an enemy. Healing in the middle of a fight is difficult, so try to position your strongest characters with heavy armor in the front and the weaker ones, more damage-based in the back.
Remember to visit your party menu to apply medication to your characters if they fall in battle. You should also check to see how many days they are going to be injured. If you want to make sure they stay out of action, you can choose to stay at your location for a day or two and wait.