Dark Souls 3 : Shield blocks fire damage from walking in lava.

Raise your shield and walk forward into the lava and your shield will block the fire damage the lava would do to you.

If you turn to any other direction other than "forward", you will take the regular amount of damage as the lava is now "hitting" you from the back.

Works best with shields that have high fire block percentage like the Dragon Crest shield.

[gnom]

Block lava when you go north only... yeah typical dark souls mechanic