When "Dark Flare Knight" is destroyed as a result of battle you can search your Deck for "Mirage Knight" and Special Summon it.
"Dark Flare Knight" is a Fusion Monster that has another Fusion Monster as one of its Fusion-Material Monsters. This makes it very hard to Fusion Summon it to the field. Luckily "Dark Flare Knight" is only a Level 6 monster, allowing you to Special Summon it with "Magical Scientist". Now you can easily get to your "Mirage Knight".