Surecast - Allow Move-&-Casting

[Khyra]

You already have this spell it's called swiftcast.

By that logic there's no reason for Surecast to exist at all (OK, arguably true heh) since Swiftcast does everything Surecast can do today + makes spells faster. (I don't think there's any way you can interrupt a spell done via Swiftcast, is there?)
Surecast is a subset of swiftcast, it would still be so if it made you immune to movement interruption, just a little less weak.
Why have it? Because swiftcast isn't always up, I guess.