Resolute Blademaster

Rally — Whenever Resolute Blademaster or another Ally you control enters, creatures you control gain double strike until end of turn.

Iroas's Champion

Double strike (This creature deals both first-strike and regular combat damage.)

Fireborn Knight

Double strike
{R/W}{R/W}{R/W}{R/W}: Fireborn Knight gets +1/+1 until end of turn.

Blade Historian

Attacking creatures you control have double strike.

Swiftblade Vindicator

Odric, Blood-Cursed

When Odric, Blood-Cursed enters, create X Blood tokens, where X is the number of abilities from among flying, first strike, double strike, deathtouch, haste, hexproof, indestructible, lifelink, menace, reach, trample, and vigilance found among creatures you control. (Count each ability only once.)