Damaging an enemy with an ability or basic attack grants Sejuani10 / 15 / 20 / 25bonus armor and 10 / 15 / 20 / 25% slow resistance for 2 seconds, increased by an additional 2 seconds per instance of damage up to a maximum of 6 seconds, with further damage refreshing the duration.
Slow resistance stacks multiplicatively from all other sources. Sejuani may achieve a maximum of 64.14% slow resistance with the Swiftness mastery at rank 5, Elixir of Iron, and Boots of Swiftness at level 17.
The Frost debuff itself is not a form of CC and hence cannot be cleansed by items or abilities that remove CC. Permafrost, however, is CC and can be removed.
Frost cannot be applied to any target affected by Permafrost until 3 seconds after the Permafrost debuff expires. Due to this, Permafrost is the only one of Sejuani's abilities that do not apply Frost.