The illusory warriors you can summon in Echoes through Amiibos are a prototype of the Einherjar from the Awakening DLCs, which are themselves an attempt to imitate Breidablik’s power.
But while Breidablik can summon the real Heroes from various worlds at their full power (being even able to summon people back from the dead), the Einherjar are weaker and don’t have total sentience of their own (their conscience is fleeting and eventually fades away, leaving only a fighter who will obey their master’s every order with no question or personality), since they are imitations and not the real thing. And the Amiibo summons, due to being prototypes, are even weaker, with them retaining even less power from the original Heroes, having no personality at all while also fading away after a short time.