When you use Gozen Match, Rivalry of Warlords, and There Can Be Only One together, you force your opponent to keep only one monster on the board, which will usually be their normal summon
It was absurdly good with other fast mana spells, letting you empty your whole hand, and then get a brand-new one
Teferi, Hero of Dominaria gives you extra cards and untaps your lands to build up loyalty along with a removal spell in the minus ability
If it attacks using this effect, the Battle Damage it inflicts to your opponent is halved
They all also generate mana of a specific color rather than colorless as a fall-back plan, and you can get them for fairly cheap
You can draw and then also toss a counter of the +1/+1type here for bigger and bigger digs from the tapping, so there is great internal synergy if you choose to mill yourself