Swords of Concealing Light
In the recent Yu-Gi-Oh! World Championship 2016, during the first feature match, a ruling issue came up when Samir Bachar played Swords of Concealing Light and Hiyama Shunsuke responded with the effect of his Dragon Spirit of White.
When the Chain resolved, Blue-Eyes White Dragon was special summoned, and then Number 95: Galaxy-Eyes Dark Matter Dragon was flipped face-down. The newly special summoned Blue-Eyes White Dragon remained face-up.
The official Yu-Gi-Oh! Card Database was updated yesterday, and the new Q&A for Swords of Concealing Light reaffirmed that the ruling at the World Championship 2016 was the correct way that Swords of Concealing Light was meant to function.
This meant that Swords of Concealing Light is very much ineffective against special summons that could be chained to its activation.
Blue-Eyes Spirit Dragon and Dragon Spirit of White could be activated in response to Swords of Concealing Light. The Dragon-Type monster special summoned will remained face-up and thus could be protected by the graveyard effect of Return of the Dragon Lords.
Mask Change could be chained to Swords of Concealing Light, and Masked HERO Dark Law would be special summoned and remained face-up.
Comparatively, Book of Eclipse is much more effective for disabling Quick Effects that special summons.
However, Book of Eclipse requires an immediate follow-up in the same turn.
Swords of Concealing Light could buy you up to 2 turns if the opponent does not have any Spell card removal effect to take out Swords of Concealing Light.
With both pros and cons to Swords of Concealing Light and Book of Eclipse, a good read and understanding of the popular decks is necessary to pick the right card for the metagame.
While Swords of Concealing Light was the more popular choice, Book of Eclipse has been experiencing a spike in recent days.