There is nothing quite like it...chest RNG

Nothing like Having 800 blue essence, and that's after rerolling 6 shards and I have yet to get a champion above 3150(besides . but no.) IP.... Also nothing like rerolling to get , then the very last order champ shard I can get for the event is . Would anybody happen to know the RNG of chest's, specifically the rarity range from 450 IP champs to 6300. and things like shards/archduke shards. got like 4 of those.