Argenport Kairos

Sure, although it's not actually an infinite loop. Basically, the way Eternal stacks triggers, the Kairos triggers will keep stacking for as long as you can put units into play without pausing. By chaining together Vara triggers, you can build up a huge pile of Kairos triggers before any of them go off. Playing Shadow units off Vara that discard cards will (hopefully) put Faceless Ones and Eldings' Pale Riders into play to create more Vara triggers, and you can keep chaining those triggers into more units that discard more Faceless Ones and Eldings. Once you have a full board, putting Eldings into play with Vara and sacrificing them to the 12-unit board limit will create more Pale Riders and more Vara triggers. If you can get several Varas into play during this sequence, you can stack up dozens of Kairos triggers before you run out of things to reanimate and Kairos goes off.

The hard part is clicking through all of this before you time out or your opponent concedes, but it's worth it when you get to watch your opponent take 30 Kairos triggers to the face in one huge burst.