Imagine the old Randuins on the reworked Sej
"Slow nearby enemies by 35% for 2 (+1 second per 100 armor) (+1 second per 100 MR) seconds"
Sejuani gains 100 (+100% total armor) and 100 (+100% total MR) when frost armor is active.

(Gargoyle)
300 armor 200 MR
With frost armor, that's 700 armor and 500 MR.
A 35% slow lasting for 14 seconds.
pogchamp