It gives Temur landfall decks another win condition, strapped to an Anger of the Gods effect
Some of these cards are very good in certain metagames and not very good in others, and its not always clear which ones to play and when (since theyre all just so good!)
Legality depends on the tournament format -- Squall, Gunblade Duelist Art Series can be legal in some formats and banned or restricted in others
This allows you to save a great deal of mana, and get a ton of value out of cards like Colossus Hammer that possess a very low mana cost, but a very high equip cost
Its not very robust since it requires you to have Ral on the battlefield and two of the same card (Expansion in your hand, but it was especially fun when you pulled it off by copying an opponents spell
Abzan is clearly the best color combination, its the most versatile, and it is the thing that people continually return to when trying to crack a stale Standard metagame