This readme is to document design decision made when implementing spells
Instead of applying the Hunter's Mark condition on enemies and then handling the movement of the mark onto others when they drop to 0 hit points, I decided that it would be easier and just as effective to apply the condition to the Ranger itself, following the assumption that the Ranger will focus it's weapon attacks on the creature it would have marked. This is based on experience of playing 5th edition D&D.
As the bonus damage only applies to weapon attacks multi-target spells are not of a concern here.
Once 11th level features of the Ranger are implemented (see Multiattack on page 38 of System Reference Document 5.1) this will have to be addressed as they allow for multi-target weapon attacks.