Arceus has come and gone and I'm torn as to whether it was a net positive or negative influence on the game due to its unforgiving stats, unparalleled combination of speed, power, and bulk, and matchless customizability that could often be frustrating. Still it was available and I tried to exhaust all the ideas I could think of so here are three teams I made with it.
Calyrex/arceus

Calyrex/arceus cores were one of the most dominant ones of the regulation and this was my take on it. I'm a fan of leads that debilitate the other team for a strong set up sweeper to come in. In this case we have scarf mimikyu with trick and the rarer gastrodon with yawn and stealth rock and a strong water/ground typing and ability (sticky hold is actually viable as well as a defense against trick) and good enough bulk. Memento is good when yawn looping isn't feasible or when they eventually concede it.
Arceus and calyrex both with Tera ground. Covert cloak is great for sacred fire mortal spin and salt cure.
Poison heal breloom is a cheesy mon against defensive Pokemon.
Archaludon with the unusual Tera of fighting to boost its body presses, especially needed for teams with both miraidon and wo-chien.
Calyrex/water arceus

Calm mind water arceus is another one I wanted to try and I though it would mesh well with specs calyrex. Bulky kyogre has been paired with caly for much the same reasons but arceus obviously is sturdier and has greater longevity.
Kyogre/fairy arceus
This is one of my favorite builds.
Standard scarf kyogre. Tera water for maximum damage output but alternative Teras are possible such as ghost since extreme speed is another thorn in its side and this was an extreme speed meta or fairy just not to be completely defenseless against scarf miraidon (especially since early in the game it was wary of clicking an electric move as described below).
If only origin pulse didn't have the accuracy it does.
With fairy arceus we finally got a physically bulky fairy with recover which was a niche that was sorely vacant. I thought it would pair well with scarf kyogre. Two of scarf kyogre's biggest pains are opposing scarf miraidon and scarf koraidon. With neat maximum physical bulk and Tera water it is good against koraidon and potentially against miraidon with calm mind, in either case often forcing teras. Taunt is good against wo-chien and clodsire (please no mental herb) which are two other common throw-ins against kyogre.
Then we have the funniest member of the team, dugtrio. I have seen some usage of it but i thought it would pair well with scarf kyogre. Of course its main purpose is to trap miraidon and either eliminate it or force a tera to clear the way for kyogre. But it also can trap eternatus or clodsire. It leads to interesting mind games when the opposing miraidon player knows you have a dugtrio in the back.
Assault azumarill is stronger against a variety of meta targets and great against Koraidon leads. Knock off is vital for removing items like choice scarf or assault vests that could get in kyogre's way.
Specially defensive gliscor to be another pain for miraidon as well as other things like clodsire and eternatus.
Kingambit as a bulky check against calyrex and eternatus. Tera ground is an unusual Tera that could be useful against miraidon. Covert cloak for Tera grass garganacl when it seems that's their main kyogre answer.
Calyrex/arceus
Calyrex/arceus cores were one of the most dominant ones of the regulation and this was my take on it. I'm a fan of leads that debilitate the other team for a strong set up sweeper to come in. In this case we have scarf mimikyu with trick and the rarer gastrodon with yawn and stealth rock and a strong water/ground typing and ability (sticky hold is actually viable as well as a defense against trick) and good enough bulk. Memento is good when yawn looping isn't feasible or when they eventually concede it.
Arceus and calyrex both with Tera ground. Covert cloak is great for sacred fire mortal spin and salt cure.
Poison heal breloom is a cheesy mon against defensive Pokemon.
Archaludon with the unusual Tera of fighting to boost its body presses, especially needed for teams with both miraidon and wo-chien.
Calyrex/water arceus
Calm mind water arceus is another one I wanted to try and I though it would mesh well with specs calyrex. Bulky kyogre has been paired with caly for much the same reasons but arceus obviously is sturdier and has greater longevity.
Kyogre/fairy arceus
This is one of my favorite builds.
Standard scarf kyogre. Tera water for maximum damage output but alternative Teras are possible such as ghost since extreme speed is another thorn in its side and this was an extreme speed meta or fairy just not to be completely defenseless against scarf miraidon (especially since early in the game it was wary of clicking an electric move as described below).
If only origin pulse didn't have the accuracy it does.
With fairy arceus we finally got a physically bulky fairy with recover which was a niche that was sorely vacant. I thought it would pair well with scarf kyogre. Two of scarf kyogre's biggest pains are opposing scarf miraidon and scarf koraidon. With neat maximum physical bulk and Tera water it is good against koraidon and potentially against miraidon with calm mind, in either case often forcing teras. Taunt is good against wo-chien and clodsire (please no mental herb) which are two other common throw-ins against kyogre.
Then we have the funniest member of the team, dugtrio. I have seen some usage of it but i thought it would pair well with scarf kyogre. Of course its main purpose is to trap miraidon and either eliminate it or force a tera to clear the way for kyogre. But it also can trap eternatus or clodsire. It leads to interesting mind games when the opposing miraidon player knows you have a dugtrio in the back.
Assault azumarill is stronger against a variety of meta targets and great against Koraidon leads. Knock off is vital for removing items like choice scarf or assault vests that could get in kyogre's way.
Specially defensive gliscor to be another pain for miraidon as well as other things like clodsire and eternatus.
Kingambit as a bulky check against calyrex and eternatus. Tera ground is an unusual Tera that could be useful against miraidon. Covert cloak for Tera grass garganacl when it seems that's their main kyogre answer.