Do you have the required heroes for the fusion ingredients?

I figured it out, Justiciar is an intermediate.

Thanks

If I already won justiciar using a shard, does that mean I would not have to fuse champions to finish that mission?

@Kalindra I honestly don't know, I've done both before the mission, so I didn't know which was counted as the one finishing the mission

No, you still have to fuse another one.