Soul Reaver is formulating a plan and would share it with the companions, but he's a bit busy right now. Hopefully the companions will subsequently be able to take some of the heat off him.
To make sure they have the capacity to do so, he's has relocated so he's in front of Sepher, so that both magical bolts are heading for him. While he's capable of solving complex problems in subtle ways, he's going to try to resolve this one by hitting it with his sword.
Blooddrinker's been sheathed in antimagic, so the incoming spells will be weakened before they even hit Blooddrinker's blade. And the blade will cut through incoming spells, draining and unravelling them.
That said, if they're powerful enough that may well lead to an explosion, not just a fizz, going off at the impact point.