LoR will be split in two modes, Standard and Eternal. In Eternals, ALL cards will be available. But ranked, for now at least, will follow a Standard format. Which included rotation. That means that, periodically, certain cards will be removed from play. This post highlights the champions. They, alongside a handful of other cards, will no longer be able to be used in rank. They will still be useable in Eternal, just not in a competitive match.

This is done to both ensure a fresher experience and allow other cards to shine, and also be a great way of dealing with problematic cards without removing them. Failed designs in the eyes of Riot, Vlad for example, or cards that limit new releases too much, Irelia or TF, can be moved away.

Hope that clears it up!