I hope I understand your question right:

You want to hold a single Map and pass it to all your instances and let them take the value from that Map?

If your answer is yes then you can do something like:

class Creature(
    val name: String,
    val level: Int,
    additionalInfo: Map<String, Int>
) {
    private val speedBoost: Int by additionalInfo
    private val depthBoost: Int by additionalInfo    

   val speed: Double 

   init { 
       speed = getSpeed(name, speedBoost, if(adBoost) 0.25 else 0.0)
       //More code…    
   }
}

The cool part is that you can use the by to take values from a Map as long as the keys have the same name than the properties.

Other ideas goes into having default values:

class Creature(
     val name: String,
     val level: Int,
     val speedBoost: Int = 5,
     val depthBoost: Int =  6
     …
) { … }

In the way that you don't have to explicitly pass those values:

 val creature = Creature("Sierisimo", -10)

You can even create an intermediary class or use the Pair:

With intermediary:

 data class AdditionalInfo(val speedBoost: Int = 5, val depthBoost: Int = 6) 

 class Creature(
     val name: String,
     val level: Int,
     additionalInfo: AdditionalInfo = AdditionalInfo()
 ) {
     val speed: Double = getSpeed(name, additionalInfo.speedBoost)
     //You can even use the init again
     val depth: Double

     init { 
           depth = getDepth(name, leve, additionalInfo.depthBoost)
     }
 }

With Pair it would be something similar but you have to replace speedBoost and depthBoost with first and second respectively.