I did some testing, and the void wyrm’s breath attack can stun you off your mount. It can also do a good bit of damage and it can be held indefinitely (the breath attack), but if you are to do so, you will consume stamina constantly over time.
The Voidwyrm is mainly used for PVP. The breath attack stuns and dismounts players. If the Wyrm has high melee damage the breath attack will destroy Tek Structures fairly quickly. On the ground it can gather thatch and cactus sap by pressing C. The eggs are also used for Basilisk taming.
Abilities wish list l. Laser breath, tranq gas breath, teleportation like astrocetus but faster, tek skiff pickup ability but a faster one, a roar to buff tek other friendly tek dinos or debuff enemy tek dinos, invisibility like the rock drake, and it will be the strongest and 2nd largest flying mount due to the Concept art.