Flaming Fist

Commander creatures you own have "Whenever this creature attacks, it gains double strike until end of turn."

Unquestioned Authority

Enchant creature
When Unquestioned Authority enters, draw a card.
Enchanted creature has protection from creatures.

Duelist's Heritage

Whenever one or more creatures attack, you may have target attacking creature gain double strike until end of turn.

Battle Mastery

Enchant creature
Enchanted creature has double strike. (It deals both first-strike and regular combat damage.)

Ajani Fells the Godsire

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Exile target creature an opponent controls with power 3 or greater.
II — Create a 2/1 white Cat Warrior creature token, then put a vigilance counter on a creature you control.
III — Target creature you control gains double strike until end of turn.

Eivor, Wolf-Kissed

Trample, haste
Whenever Eivor, Wolf-Kissed deals combat damage to a player, you mill that many cards. You may put a Saga card and/or a land card from among them onto the battlefield.

Spirit Mantle

Enchant creature
Enchanted creature gets +1/+1 and has protection from creatures.

Blood Mist

At the beginning of combat on your turn, target creature you control gains double strike until end of turn.