Spells or abilities that allow you to divide a single instance of damage between multiple targets can only target the nemesis or a given minion once. For example, this means they cannot be used to remove multiple shield tokens from a minion or multiple nemesis tokens from the Magus of Cloaks. The damage is all dealt simultaneously, so everything targeted must be a valid target at the time the spell or ability is evaluated.
This is not true of spells that deal multiple instances of damage (e.g. Echo spells).
