Wizkids Rules!

Tetch:

When Jervis Tetch attacks, gain control of target opposing character die with purchase cost of 4 or less. That character die must attack this turn (if able).

Knowhere

You may swap any character die in your Used Pile or Field Zone for an unpurchased character die costing 1 more (return the swapped die to its card). Character dice swapped in the Field Zone stay on the same level.

Can you use Jervis Tech to take control of an opponents die, then use Rare Knowhere on it? If so what happens to that die?

There are a few ways people are interpreting this.

1) The knowhere triggers and the controlled die is sent back to the card.
2) The knowhere triggers and the controlled die is sent back to the field.
3) The knowhere triggers and the controlled die is sent to the prep area.

stevomuck wrote:Tetch:

When Jervis Tetch attacks, gain control of target opposing character die with purchase cost of 4 or less. That character die must attack this turn (if able).

Knowhere

You may swap any character die in your Used Pile or Field Zone for an unpurchased character die costing 1 more (return the swapped die to its card). Character dice swapped in the Field Zone stay on the same level.

Can you use Jervis Tech to take control of an opponents die, then use Rare Knowhere on it? If so what happens to that die?

There are a few ways people are interpreting this.

1) The knowhere triggers and the controlled die is sent back to the card.
2) The knowhere triggers and the controlled die is sent back to the field.
3) The knowhere triggers and the controlled die is sent to the prep area.

No. You may not use Knowhere to swap out a character die your opponent owns for a die you own.