If there's any creatures with First or Double Strike involved in combat, then as the combat damage step starts, only those creatures will deal. Because Double Strike technically gives the creature first strike then a second strike during regular combat does it still hit first against a creature. An explanation of the " First strike " and " Double strike " abilities in the Magic: The Gathering Trading Card.
It doesn't stack with first strike since the first combat damage step considers both at the same time. This means that triggered abilities that trigger on hit happen twice with combat damage. Deflecting Palm and Dictate of the Twin Gods Trinisphere vs. Rules Guru Valar dohaeris. The only creatures that assign combat damage in that step are the remaining attackers and blockers that had neither first strike nor double strike as the first combat damage step began, as well as the remaining attackers and blockers that currently have double strike.
Double strike first strike Video