Attacking creatures you control have double strike.
"So you see, the reckless battle strategy of the Kathorran orcs was effective, but ultimately proved to be a double-edged sword. As did their double-edged swords."
2021-04-16
If Blade Historian leaves the battlefield after first-strike combat damage has been dealt but before regular combat damage (perhaps because it attacked and was destroyed by first-strike combat damage), attacking creatures you control will lose double strike. A creature without double strike won't deal regular combat damage if it already dealt first-strike damage that turn.