The goal of the deck is to play creatures and slap counters on them with cards like Maester Seymour then reward you for doing so, drawing you cards with Bred for the Hunt, giving them keywords with Sphere Grid, or protecting them with Inspiring Call, all while your creatures to continue to grow and bash in for more damage
Here is the decklists for the Commander precons for Adventures in the Forgotten Realms
If it prevents damage, Comeuppance (not the original source) deals damage to the permanent or player as part of that prevention effect
Merfolk is a relevant Creature type if youre already messing about with them in Commander, but its not relevant to why this card is so good
Cards that duplicate your serpent tokens are great too since your commanders activated ability requires serpents to sacrifice
The Sixth Doctor copies the first historic spell his controller casts each turn