"It also works as a Tennis Raquette!"

Grindix-Birvikaan, AKA: Slugbutt. Now, this guy is considered one of the more competitive of the pair, with plenty of brawling potential and bonuses, and overall a good list of abilities.
To start from the bottom, he has what I consider the more confusing abilities on him: Super Stomp. Now, questioning because of his figure, how does someone with a Rear end that drives along on a series of smaller drillbits somewhat like a centipede, STOMP?
No matter. It makes for good power dice generation. Set up a few cheap structures in a corner, like Office Buildings, make a stomp and have plenty of power dice for an impending double activation.

Next ability up the ladder is Red Distract. I can understand why he has distract. Anyone close enough to him will be wondering the same thing (I.E. "Slugbutt does what now?") and that's bound to throw them off their attack ever so slightly. I like distract. It goes great on a Unit, especially one that really tears up the town. Like the Cthulubite. I won't say that it's as good on a monster, but that's because they could never live up to the Cthulubite. Nothing can live up to be a Cthulubite.

Third up is the staple ability of the mole people: Burrow. What a surprise.

Now we're onto the Offensive Triggers.
Slugbutt is a brawler, and you can tell by the giant buzzsaw as one hand/arm/limb, and I have no idea what his other is. I know it's not a blast attack, because he doesn't have one.
He has three triggers. Two are old reliables, Power Drain and Lightning Attack, and his new ability is thus:

Synchronized Move—Choose 1 allied unit within 2 spaces of this figure and advance that unit up to its SPD, even if it has already advanced this turn.

Power Drain is self explanatory - Hit a monster and he loses a Power Die. Synchronised Move is interesting in that you can move units to block an attack alley and force your opponent into a particular type of attack. Or move a unit adjacent to you for their Red Ability, or aura ability (like weaken) on your Second Lightning Attack.
Lightning Attack is a debatably better form of 2 damage compared to Super Damage:

Lightning Attack—Once each turn, this monster can roll a second attack of the same type with dice in play against the same target monster.

It is difficult to negate. It is also another attack, all other triggers are triggered again.
Power Drain takes away another Power Die, Synchronised Move denies another avenue of attack. And yet there are more Brawl Triggers that can be added to Slugbutt.

The Sports Arena has "Energy Drain - If target monster is hit, move one 1 A-die to the unit pool."
The Elite Corruptor has "Overload - If target monster has more than 5 P-die in it's pool, this attack deals Super Damage."

Thats right. Two A-die, Two P-Die, up to two moved units and Four damage later, you have finished your turn. And because it's Lightning Attack, the dice provided in the attack would be a Surplus of Power Die that you can gain back easily with the A-die you kept in your pool for a double activation.
"Wow, that IS powerful!" exclaimed every other player who hasn't figured this out.
"Yes, yes it is!" says the official announcer, proud of this seemingly overpowered combination.
"What's the catch?" pipes up the one suspicious fellow who always hides up the back of the crowd to hear his own thoughts.
Well, obviously it's having to secure the Sports Arena and having an Elite Corruptor within two spaces of Slugbutt.
Difficult? Only a little.

So we move onto Ultra Slugbutt... Boy am I liking this name... who changes his Brawl Triggers while keeping the same play.
Replacing his Power Drain is Energy Sap. This is much the same as Energy Drain, where it moves an A-die to the opposite pool, however it also applies to units. If you were to brawl an enemy unit, you can choose to move an A-die to their monster pool. It can deny a unit spawn or a Unit move. Or you can stick with hitting a monster and draining an Action die from it. With Energy Drain from the Sports Arena, Two Action Die are torn away from their grasp.

"Why would I go into this form if I can do more in my alpha?"
Because there is one other trigger available to you in the Ultra form:

Grind—Move 2 A-Dice from the dice in play to your inactive pool. Then move 2 B-Dice and 2 P-Dice from the dice in play to your dice well. If the dice in play include at least 1 remaining A-Die, roll another attack of the same type against the same target monster with the remaining dice in play.

With a Brawl stat of 8*4, this offers up to 4 attacks. Four Action-die shifted back to the Unit pool, Eight if your sports arena is secured.
Four potential damage, Eight if you have an Elite Corruptor adjacent.
Denying a Whole turn and Form is, however, not bloody likely. To have above a 50% chance on all the attacks, your oppoent needs to be Defence 5. Granted, this isn't hard. Spawn a Cthulubite and an Elite Corruptor and your opponent is already lowered by 2, and you have Overload available.
To get to 8 Action dice denied, however, your opponent needs 7 health or more, which leaves us with the following figures: Gorghadra, Ultra Xaxor, Mucustos.

"Should I really go through with something so major?"
In my experience, No. Attempting double activations seems difficult, but is possible. The difficulty lies in keeping a power base that hasn't been ravaged by your opponent, and conserving dice. Because the attack decays after each other, one must compensate for the said attacks. Played as if it were Lightning attack, with a few more power die than usual of course, Slugbutt runs around bugging the crap out of whoever he wants, and taking 4 Action Die with him each turn, denying your opponent his own double activations.

In conclusion, I find personally that Grindix-Birvikaan is better off in his alpha form with his Lightning Attack/Synchronised Move/P-die denial set rather than his Ultra form with the Grind/A-die denial abilities. In a Two Monster Game, while Drillnose runs around tearing up the opponents power base and gaining power dice, Slugbutt runs around on the offensive going willy nilly on the opponent.