Rockantium

Rockantium was the first earth-type Legendary monster. He is slow, but can be very dangerous.

Overview
Unlike other terrible monsters like Nebotus and Thundhare, this monster is bleh, but still better than those two, but jesus, he is sooooo SLOW, he will be outsped from every monster you may encounter, even though he has no stun or Hardened trait, he will almost always be Stunned, Freezed, or Possessed. Basically it will be easy for foes to kill him before he uses any attack. But still, he is not a bad monster, since he has an alright Attack stat, and may at least kill one foe. Seriously though, he will not be necessary in a future, just give him Gold runes instead.

Pros
 * Decent Skills
 * Not many cooldowns
 * Pretty good Health
 * Not bad Strength
 * Stun moves

Cons
 * 2nd Slowest legendary. (slowest - Worker Hulk )
 * Bad trait.

Recommended Moveset
He have no choice but simply get outsped and die, but to make him at least survive a turn and go for Protect all Team, then give him Life runes. But since he'll most likely get stunned, frozen, or possessed, 3 Speed will at least give him a chance, since he is a stun debuffer, to outspeed and at least stun one Dark monster that doesn't possess the Speed runes and attack other monsters later, and if you have WAYYY better supporting monsters for example General Thetys or Nishant's Pet, go for Team Speed, this gives them the extra speed to at least outspeed other monsters that has higher base Speed and give debuffs while a other better Attacker can outspeed and OHKO or severely damage all foes with an AoE move and Rockantium can at least clean up any remaining foes, or simply go for Team Strength if you have problem with your Attackers and want them to hit harder.
 * Rock Avalanche
 * Stone Rod
 * Rockorites
 * Protect all Team
 * 3 Speed; 3 Team Speed; 3 Life; 3 Team Strength; 3 Gold ( Most Recommended )

Counters
Since he has a horrible Speed stat, he can be outsped by any Dark monster and be eaten by them for dinner, regardless if they use Strength runes. You can also simply Stun, Freeze, or Possess him and chip his health away bit by bit. Basically, any monster that's not Thundhare or Lagerchaun could kill him. Forget about it, Nebotus could probably still die to an element he's strong against.

Island Offer
Rocktainium is the very simple beginning legendary pack. The simple answer is no, do not get him. First off, he's a bad legendary, and second off, you can later on breed him. If you're THAT eager to get a legendary, then go for Exo Skeel, and if you want a better attacker, and a faster one, go for Killeraptor.