Jumbling Jester will swap the highest amounts of Attack, Armor and Culture with the lowest amounts on any cards on the board. This ability will only activate when the card is initially drafted. The effect will carry over to subsequent rounds.
If you plan to use it, try to stack low value cards such as 1-damage military and negative culture underworld cards before it gets dropped.
If you have it as a possibility in the final round, don't drop any "maximum" stat cards down until you play it (i.e., healthy walls, high culture cards, high attack cards, etc) and try to play cards that will win the "minimum" stat position.
Overall, this card is very random and unreliable.
Jumbling Jester turns temporary stats into permanent ones after swapping. i.e., If a Berserker with 2 attack (from 1 enemy) swaps its attack value with War Elephants (9 attack), Berserker will now have 9 base attack, plus 2 more for a total of 11 attack. War elephants, however, will be down to 2 attack. A similar mechanic applies to Great Council and Fort of Last Resort.
Boosts from Reinforcements are pending.