If most of the enemy is squishy and mid health champion,take Shadow assassin as it will be easy to as it will be to assassin them
If enemy`s tank is fed use rhaast as it will use their maximum health as damage

If u gank tank champions like Garen,Nautilius,Alistar, U will get souls to become darkin which is useful to 1 v 1 tanks.
If u gank squishy champion like ashe,teemo,etc.U will get souls to become shadow assassin which is useful to assassin them

If u use E outside the wall, the duration will be shorterned
If u use E inside the wall, the duration is normal.