Bright Lance

The Bright Lance is one of the most powerful heavy weapons in the arsenal of the Aeldari and is an equivalent of the Imperial Lascannon in utility and power. It can be added as an optional weapon to Wraithlords, War Walkers, Falcons, Wave Serpents and Vypers. It operates in the same manner as a Lascannon, firing a concentrated blast of coherent light that is primarily intended to destroy enemy vehicles. The Bright Lance is a far more efficient weapon than its cruder, human-made counterpart, in part due to its use of psychically-grown crystals to serve as a lasing matrix. It also possesses greater accuracy than a Lascannon and can penetrate any form of armour that is less than a certain thickness.

Sources

Codex: Eldar (7th Edition) (Digital Edition)
Codex: Eldar (3rd Edition), pg. 46
Codex: Eldar (4th Edition), pg. 22