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I don't mean as in as much as you want per turn but as many times in a game?
No. read the rules for it, you roll a double, thats it, no more guants.
Your friendly neighbourhood gargantuan creature
it's not you, .. it's me. i just need some space. things just... arnt' working out between us.
if you don't role a double though conceivably the tervigon could go on producing termagants every turn in huge numbers as long as you have enough models to cover it.
The potential output of a tervigon is between 3 for the game if you are incredibly unlucky and 15 a turn if you are king of the dice!