As the attacker with focus, can I play Void Seeker and then Stupefy on the same stack without giving my opponent a chance to respond, and would this prevent Void Seeker from being countered?

Ruling: You can play Void Seeker followed by Stupefy without passing priority between the two (you hold priority until you choose to pass it). However, Stupefy does not prevent Void Seeker from being countered, as counter spells can target any spell currently on the chain.

Sequence:

• Attacker (not turn player) gets focus first
• When you play an action/reaction, priority is always passed between both players when an item is added to the chain, starting with the person who added it
• You can hold priority and add multiple items before passing
• The chain resolves one by one, and players can keep adding items as it resolves

Nuances:

• Focus does not determine playing Reactions, Priority does
• Turn player does not determine who gets focus first - it is always the attacker
• There is no "chain blocking" like in other games - counter spells can target any spell on the chain, and opponents can wait until a spell is the next item to resolve before countering it