This RAID tip / warning is for those players who are working on their Arbiter missions.
A little before reaching the Arbiter there is a group of missions (see picture below) which require the players to Ascend champions of 4 affinities to Level 6 of Ascension.
These missions are not retroactive, so if you already have the 6 star fully ascended champions those will not count!
Therefore, as you make your way towards your Arbiter remember to prepare 1 champion of each affinity without the last ascension. Yes, this means you cannot use a banner temporarily, but if you don't prepare then you have to create 4 completely new 6 star champions which can take a long time (usually about 1 week to make 1).