Double Strike vs Regenerate Regenerate means that instead of a creature being destroyed, it becomes tapped, all damage is removed from it and it is removed from combat
You dont get an immediate buff as you do with a traditional typal lord, but its buff sticks around should this creature die, plus it invites +1/+1 counter synergies to the party
The latter is a 1/4 defender common for four mana that cannot swing but rocks evolve to rock the block defensively as you have loads of stuff with power greater than 1 to grow it over time into a big threat
Finally, and as always, I can't wait to see you in the queues
Grand Arbiter Augustin IV only decreases cost if it has colorless mana, but theres none
If a card has no mana cost, its escape cost is an unpayable cost, so you can't cast it for that cost