Ultimate Castle Golem in my opinion is a very useful card for every type of deck, but especially the Blue Color Deck. I think so because of its devastating BP and also the very useful effect it has. It comes with a Core Cost of 7 that apparently seems high, but it comes also with a Cost Reduction of 3, so you can deploy it , if you have the right cards, at Core Cost 4.
Well, to talk about the function of this card in a Blue Color Deck, we need to talk about firstly about the ability of the Blue Color Deck. The priority of this type of Deck is to destroy the opponents deck. That is why Ultimate-Castle Golem can be really useful in this deck. Its ability of all the three levels it has (Level 3,4,5) is very special, because when your Trigger Shot hits your opponent has to discart cards from his deck equal to the Core Cost of the card triggered multiplied by 3. Since this Ultimate has a high Core Cost it can be be very easy do hit. Also this Ultimate has also a very high BP since it has 11000 BP with only one core at the first level (Level 3). The other levels are a little bit difficult to use since they need 4 Cores (Level 4) and 6 Cores (Level 5), but if you use the typical Blue Strategy (Deck Destruction), you will not need power, but only its special ability. For example when you hit a card with a Cost of 5 or 6, you destroy one third of your opponent deck.
Strategies and game play:
I strongly suggest to use this card with low Cost cards. You can find out some Low Cost Spirits that can be also very useful such as: Riot-Golem, Quartz-Golem, Javelin and some other spirits that have Charge (This is a ability of Blue Spirits to increase the number of cards discarded to trash by the ability of a blue spirit or Ultimate by 1 or more). Next this spirit must be used with nexuses such as: The Sapphire Sculpture or The Rare Metal Mine. This last has the ability to make you opponent discard 3 additionally cards when he pays an attack with his life. (This ability can be used in level 2 but the level 2 needs only one core so it is easy to upgrade the nexus).
Combos with other cards:
One perfect combo with this card needs this cards:
Ultimate-Castle Golem (Optionally two times), Maximum Break, The Rare Metal Mine (Level 2), The GreatFist Roger, The HeavyJavelinGiant Lance, Riot Golem.
Maximum break can be deployed at Cost 4 with Cost Reduction so if you are in the 10 or higher turn if won't be a big problem. Next your Castle Golem can be deployed at Cost 4 itself. If you attack with Ultimate-Castle Golem Trigger activates and if you hit for example Cost 5, your opponent discarts 15 cards, but thanks to Maximum Break, he/she discards other ten cards. Then by the effect of the two spirits he discards other two cards. Then if he pay with life he discards other 5 cards (3 by nexus and 2 by Charge). Next it is Riot-Golem turn that if attacks it get a total of cards equal to its level. Let's suppose it is at level 1. So 1 card plus 2 from charge. This combo needs minimally 5 turns to be deployed so you need cards to guard yourself. I suggest Burst Wall (3x) and Dimension Sword (1x). So 15+10+2+5+1+2=35. You just destroyed 35 Cards. If we consider that we are at the 5th turn your opponent has used 10 cards so you destroyed a 45 cards deck in a turn.
Ways to counteract it:
Since this card need a few Cores to Grow up at level 4 or 5, many people use it at level 1, and that is not a mistake, but unfortunately the Purple Color Deck has a priority of draining cores and Ultimate-Castle Golem can be an easy objective. That is why Purple Deck beats almost every time Blue Deck
At the highest level this Ultimate reaches a BP of 26000 which is very high. Also as we talked before its ability is very devastating. So we can say that this is its Strength, his own ability. For power decks such as Red and Green this Ultimate can become the key of winning but, for strategy decks such as White and Purple it can be very difficult;t to use in the proper way this Ultimate
The only weaknesses I can say about this card is the Core Cost because 7 can be sometimes easy to guard during the trigger. Also a very negative thing is that you need about 6 cores to grow this card at his highest level. But with 6 cores, with cost reduction you can play another Spirit, Ultimate or whatever you want. So it is a big deal.
This card has been seen in the latest anime series of Battle Spirits, Ultimate Zero, and its user is Kiriga, who uses himself the Blue Color Deck.
Artwork and aesthetics:
About the art work I can say that its a very "pretty" card and also in the anime it seems like a moving giant castle, which means this cards is very powerful and destructive.
If would give this card a rating I definetly would choose 8, because it is very ppowerful and woth the right combos it cann give you the victory but it is not an invincible card, so just for now ill pick 8.