Red is usually paired with blue, that can support the monkey with Countermagic
Overall, the keyword makes sense and belongs in this deck
Your opponents can collude to weaken the impact
The effect of Max Balloon is useless against most of the field, but it does wall out the odd deck that only uses Basic attackers such as Regigigas and Blissey/Miltank
Initially printed in the 1999 set Portal Three Kingdoms, Imperial Seal received a reprint in Double Masters 2022, along with a foil etched version at a higher rarity
On the other hand, to your point about synergies, Ghalta-Atraxa-Tortoise was a very syngerstic group, and people hated Gregs ability to pilot it so much that all three got nerfed