How exactly does Ancient Blade work? it says: Bearer must be an companion. Each minion gains this ability: 'Assignment: Assign this minion to bearer of Ancient Blade.' Regroup: Discard this condition to discard a minion and reconcile your hand.
So if there is 2 or more minions played and they all gain that text your opponent has no choice but to play all minions on the bearer of Ancient Blade, or if not your opponent you do. Sorry to be so confused on this card.
TLDR: the shadow players may assign any 1 minion to skirmish the bearer of
ancient blade, then assignments happen as normal.
From the Comprehensive Rules: "Many assignment actions assign a minion to a companion. You cannot do this unless both of them are unassigned."
The way the assignment phase works in general is this:
1. Players take turns using assignment actions on their cards
2. FP player assigns unassigned minions to unassigned companions (or allies at their home site). If any character is defender +X, they can be assigned up to X additional minions beyond the first
3. The shadow player(S) assign any remaining unassigned minions to companions (or allies at their home site)
Special abilities are optional, so the shadow player could choose not to use the special ability that
Ancient Blade gives their minions. If the shadow player uses the ability on minion 1, then they can't use it on minion 2 because by that time the bearer of
ancient blade is already assigned to a skirmish. If the shadow player doesn't use an assignment action to assign a minion to the bearer (or if the bearer is defender +X), then the FP can assign that companion as normal. If there are leftover minions after the FP player finishes assigning, then the shadow player can assign them wherever they want to, including ganging up on the ring-bearer or the bearer of
Ancient Blade.