scareclaw yugioh deck Light-Heart - Power of the Elements You can only use this effect of Scareclaw Arrival once per turn. SCARECLAW DECK 39 | Primitive

This locks down the effects of link monsters entirely because they cannot be placed in defense position

While many players will still choose to build tier decks, the free cards from Golden Packs and the overall decrease in the cost of playing constructed on Arena might free more players to build fun decks or rogue brews since the risk building a deck that isn't successful is much lower since building a second deck should be much cheaper or less time consuming

And with this last one, we get to the end of the list

Mana Drain One of the most iconic counterspells in Magics history, Mana Drain not only nullifies a spell but also provides you with mana equal to the countered spells cost during your next main phase