Hello everyone and welcome to my 150th analysis, this time featuring Osteoclast.
Overview: Osteoclast is a perfect monster for a Calendar, because while he isn't going to dominate any time soon, he can dish out damage and is a very powerful addition to the teams of beginners. As stated before, Osteoclast can definitely dish out good damage, and given the right allies he can even win you games, which I will get into later. On top of this, Osteoclast has a method of getting rid of any non-control status efect on him, given that the enemy has no Anticipation monsters. However, Osteoclast is hopelessly outclassed by Narok, who has Anticipation on top of Stun Immunity, and many other monsters are far better choices than he is, plus he is extremely slow and frail, which prevents him from functioning against the general populace of monsters.

-Ossein Slashes
-Bone Shell
-Bone Power
-Skeleton Army
Runes: 3 Strength
Mutant Rune options: Strength&Life
Relics: Masks

Build Explanation:
Osseins Slashes hits hard with 65 Base Power and it Stuns the target. Bone Shell can be spammed over and over again to serve as a pseudo debuff removal. Bone Power is a simple power boost, but it's a great increase in power that necessitates the opponent's attention. Lastly, Skeleton Army is his strongest AOE.
Osteoclast must deal as much damage as he can when he moves, so 3 Strength Runes are the best choices on him to maximize damage.

Teammate Options: If you can get Skill Mirror on him, you can use Bone Shell to get 2 extra turns. This will allow you to use Bone Power followed by Skeleton Army to hopefully kill all enemies or at least greatly damage them. Warmaster Remntar is a perfect teammate for this reason, as he also protects Osteoclast from being damaged by Special moves. For more Teammate options, check out this article.

Countering Osteoclast: For Counter options, check out this article.