Riven can dodge Tahm Kench's devour damage.

If Riven presses E immediately after Tahm consumes her, she will not take any damage from Tahm's devour. It happened twice in the same game. The shield does not absorb most of the damage, it completely negates all damage dealt from devour.

A maxed out Riven shield should still be broken by the high percent magic damage that devour inflicts on the target and damage should be dealt to the champion's health. This is not the case.