How does Svellsongur work with activated abilities that have exhaust costs, specifically does it double the values (e.g., will Lux give 4 energy instead of 2)?

Ruling: Svellsongur does not double the values of activated abilities. It gives the unit two instances of those activated abilities with the same text.

Sequence:

• The unit gains duplicate text of its activated abilities
• You can only exhaust the unit once per activation
• Exhausting the unit is the cost of using one ability
• You cannot pay for both abilities with one exhaust, just like you can't spend the same energy for two different abilities with energy costs
• If you ready the unit, you can exhaust it again, but this is already true without Svellsongur

Nuances:

• Equipment grants its effect text to the unit as a matter of how equipment works, so you cannot exhaust Svellsongur itself to use the ability