The fusion circle would probably cause you to immediately be branded traitor by both gods. And of course, you'd have to rick losing dominance to the other player. And have to get them into the circle in the first place.
My gods are:
The Sower of Seeds. Worship by: Plantng seeds, preferably in the corpses of your enemies. Boons: Food, Healing, Specialized Plants. Taboo: Use of Fire or Metal. Curse: When you touch them, plants either wither and die, or they mutate and attack you.
The Breaker of Spells. Worship By: Destroying magic Items, killing mages. Boons: High quality items that resist magic, buffs Taboo: The use of magic or anything made by magic. Curse: You become weak and frail.
The Consuming Flame. Worship by: Burning things Boons: Buffs Taboo: Seeing someone or something you can burn, and not trying to burn it. Curse: Slowly freezing to death.
The Weaver of Flesh. Worship by: Cutting yourself, cutting your enemies, eating your enemies, etc. Boons: Mutations, Minions, Healing. Taboo: Destroying flesh. Cutting, crushing, or eating it is fine. But don't burn or disintegrate it. Curse: Wasting away.
The Sage. Worship by: Seeking out new knowledge. Boons: Knowledge. Taboo: Destroying knowledge. Curse: Being struck blind or deaf.
The Master. Woship by: Tricking people, Controlling people. Boons: Minions, Things that give you the ability to control other people. Taboo: Obeying people of other faiths. Curse: Being forced to do what other people tell you to.
The Smith. Worship by: Making things, preferably things noone has ever made before. Boons: Tools, Raw Materials. Taboo: Destroying Items of good Craftsmanship. Curse: Being unable to create.
The Betrayer of the Living. Worship by: Killing living things, making unnatural creatures. Boons: Magic Items, Healing, Knowledge. Taboo:Sparing a living thing. Curse: Being unable to Heal or regenerate.
@ GWG: I mean make a sentient flesh human that you control, and have it worship a different god then you. There are lots of risks, or course, but it could be attempted.