The warding bond spell states:
(…) Also, each time it takes damage, you take the same amount of damage. (…)
The tether essence spell states:
(…) When damage is dealt to one of them, the same damage is dealt to the other one. (…)
Let’s assume that Alex and Bailey are bonded together and Alex cast the spell. This is a one-way feature so if Alex took damage, nothing special happens and if Bailey takes damage it is first halved (due to the resistance) and then Alex takes the same amount of damage.
Let’s assume that Alex and Bailey are tethered together. It’s clear that tether essence cannot activate off of its own damage; in other words, if Alex took damage, Bailey would then take the same amount of damage and it would end there. Alex would not take the damage Bailey just took.
These cases are rather clear and straightforward, but happens if they are bonded and tethered together? Say Alex cast warding bond again; what happens if Alex takes damage? Bailey takes the same amount of damage and then…? Does tether essence activate? Does that make warding bond activate again?
What if Bailey took the initial damage: Does warding bond activate or tether essence or both? If warding bond activates does tether essence then activate from the damage that Alex takes?
What happens when both of these spells are active on the same two creatures and one of them (either the caster of warding bond or the other one) takes damage?