Flashing Swift (閃神速；Senshinsoku) is a keyword debuted in BS59, currently exclusive to the Revival version of The BlackInsectDemonLord Diabolica-Mantis. It's a variant of High Speed. The wording is as follows:
- Flashing Swift - Then, if you paid the cost with cores only from the Reserve during either Attack Step, you can summon it without paying the cost.
Flashing Swift only exists within an Accel effect, so the "cost-paying" part refers to the Accel cost. It gives the Spirit the ability to be immediately summoned after its Accel effect instead of staying in the Removed Zone. Plus, since the keyword is "Swift"-named, the Spirit can also benefit from effects which support the related keywords.