Rule 478.1.c
If a dependency chain loops back around on itself, identify the minimum set of Game Objects in the loop and evaluate their layer effects simultaneously, layer by layer. If any of them have Game Effects that reference Game Objects from outside the set, pause and evaluate those Game Objects first before continuing with the set. Example: A 4 [M] unit reads “If there is a [Mighty] enemy unit here, I have +5 [M].” Both players control one of these units at a battlefield during combat. Each one is buffed. A third player plays Siphon Power, which reads “Choose a battlefield. Give friendly units there +1 [M] this turn, and enemy units there -1 [M] this turn, to a minimum of 1 [M].” Both of the units there are given -1 [M]. Because they have effects that reference each other, they have a dependency chain. After evaluating their layers simultaneously, layer by layer, both units will be 4 [M].