Honestly, I think abyssal scepter is a better second MR item on Mundo than Banshees Veil

Keep in mind, it's not very often you'll find yourself itemizing two MR items on mundo since you're typically stacking HP and armor to tank adcs indefinitely. But in scenarios where two mr items are an absolute must (like Cass or Ryze), I honestly find abyssal to be better overall.

For starters, it's only 5 less MR than banshees. Typically, a mundo build is going to be Tabi, Sunfire, Thornmail, Warmogs, Spirit Visage and Randuins against a team that you feel like the HP is sufficient enough at dealing with the enemy AP. But when you want that extra MR, you can swap out randuins and still be in the neighborhood of 4k HP. Sunfire and Thornmail plus mundos damage from W and Q are all magic damage, and outside of Q (and even then in most cases you're in abyssal debuff range when chasing), you're in abyssals debuff range. This only helps those do more damage as its reducing your MR and mundos W DOES have AP scaling, abyssal alone won't make it too overbearing but every little bit helps.

The amount of damage you can end up doing with this is pretty absurd honestly, it's not burst damage by any stretch but you're burning everything down slowly as you're sitting on top of the enemies faces Mundo-ing away. It's legit, trust me.

Get your freelo now