Remove 2 counters from your Resource Prevent all damage to one of your Characters and retreat it. Play only if that Character would be discarded.
Keywords
Switch
Switch: [1st/2nd/3rd type effect]: A layered, static ability that means, "As long as this unit is in the first arena listed on its type line, it gets the effects listed to the left of the first slash. As long as this unit is in the second arena listed on its type line, it gets the effects listed to the right of the first slash. As long as this unit is in the third arena listed on its type line, if any, it gets the effects listed to the right of the second slash, if any." If it says "None" as one of the arena type's effect, it means that it gets no extra effects while in that arena. The unit's Switch effects will correspond to the types listed on the unit's type line. There won't be a slash for an arena not listed in the unit's type. Switch doesn't allow units to change arenas during the battle phase.