The mechanic needed an errata that fundamentally changed how you played with them, but even that wasnt enough to save multiple companions from the all-powerful ban hammer
That means that even if you have a copy of Gideon, Battle-Forged in play, you dont have to fear losing one of them to the legend rule as long as you keep Kytheon, Hero of Akros back on defense a game he is prepared to play
In the past with just Kuldotha Rebirth it usually wasnt worthwhile since your odds of drawing a Kuldotha Rebirth wasnt especially high and cards like Ornithopter and Memnite are pretty bad if they aren't turning into three 1/1 Goblin tokens, but now the odds are in favor of having one in hand every game
If you can cast a spell with delve from your graveyard using flashback like the ability from Snapcaster Mage, you can apply all the rules from the mechanic
This year for North America and Europe there 2 Finals, in Sept.-Oct
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