Furthermore, you CANNOT buff Seraph and then shield it again it UNLESS you allow your opponent another turn to slay it, which is probably not what you were going for. The immaterial status lasts until the end of your next turn, but it fades slightly allowing you to reactivate the ability. It is still immaterial at this time however. If you're going to buff it, it's probably best to do it BEFORE you shield it the first time. Just thought I'd clarify this in case anyone misunderstood.