Atarka, World Render

Flying, trample
Whenever a Dragon you control attacks, it gains double strike until end of turn.

Darksteel Plate

Indestructible
Equipped creature has indestructible.
Equip {2}

Darksteel Ingot

Indestructible (Effects that say "destroy" don't destroy this artifact.)
{T}: Add one mana of any color.

Rith, Liberated Primeval

Flying, ward {2}
Other Dragons you control have ward {2}.
At the beginning of your end step, if a creature or planeswalker an opponent controlled was dealt excess damage this turn, create a 4/4 red Dragon creature token with flying.

Palladia-Mors, the Ruiner

Flying, vigilance, trample
Palladia-Mors, the Ruiner has hexproof if it hasn't dealt damage yet.