Nice video showcasing this team.
I’ve run a very similar team to this for quite a while. One of my favorites in fact:
Black Beast***/Ettin***/Green Seer/Giant Spider**
Ettin’s Empowered column destroy and huge attack boost on turn 1, with higher base life than anointed one and both having similar attack and life after casting once, and the fact that it doesn’t make a bunch of useless reds, coupled with being able to charge green seer a bit to get things started, make it a better choice in my opinion for this team. Other worthy options are Archer with Mang (with fast, purely to get a massive attack boost to start the carnage) or Anu’s Scepter (usually take yellows to fill seer, then start looping). Manticore would be nice to put here, but if you have it traited to Empowered, it also has Impervious, and you can’t devour it even with your own Black Beast.
You want Beast in the first slot because using converters can align skulls for you, and the fact that he heals to full after every devour. The very act of summoning the spider can occasionally align some skulls for huge damage. You can err on the side of caution, but also keep in mind that a troop that has been damaged only transfers its remaining stats to the beast when it is devoured, so you are both making your team much slower and your beast easier to kill in the long run. If your beast dies, the team is relegated to spider swarm zerging while using converter loops to drop skulls either way, so you really want those huge stats. If you get skull cascaded to death in the two turns before you can get green seer up for the first time, things have to really not be going your way already.
AI Great Maw does not counter this team on PC/Mobile. You charge far, far faster than them them and every subsequent turn after green seer/spider is up is spent trading skulls. Even though maw has an amazing skull trait, Beast gets much bigger, much faster, and that is if it doesnt just kill maw outright when you devour your first team member. You obviously wouldn’t use a team like this on defense, so a player could never just make the decision to Maw devour the black beast and make the team worthless, you are playing versus an AI that hopelessly take skulls over and over while overall making no impact.
The team is countered by entangle (hard, do not use it versus entangle), freeze (more annoying, but can be a problem), and instant kills (death touch, bullseye, assassinate traits). Shadow Hunter might be a problem, but a buffed beast that has some armor left and having the second slot empty when it casts makes it survivable usually. Stoneskin and the like are pretty much speedbumps.
One small note on usage: if there is little converter mana left on the the board, or the enemy has a board mod spell ready, it is usually more beneficial to gather that mana and just let your opponent take skulls until the beast can kill. You also don’t want to be converting away purple or green unless absolutely necessary. Having yourself or the opponent get green or purple off the board usually stalls you unnecessarily while waiting for your mana to reappear.