Ok, so solstice can at most deal 6 damage without actually attacking, which is not enough to kill either Sam or Araches. This means that we can just cast poison on Solstice and sit around until he dies or dispells it (or see if he dispells manashackle), since Araches and Sam are surrounded on all sides by (soon to be) corpses and edges of the map. After solstice is dead (or uses the dispell), sam can manaflare Araches and then Lightning every round for the win.