The Checkered Rookplate is a Air/Spirit Shadowforged Armor. It is effective against Water/Earth armors, but ineffective against Earth/Fire armors.
Upgrading the Regular version of this armor to level 99 achieves stats of 3412/3001, and it is 46/44 additional stat points for each Ascension level thereafter (so 5 Ascension levels would result in 3642/3221 and 10 would reach the maximum of 3872/3441). The Special Ability chance is also increased as well, from 8% at Ascension level 1 (level 99) up to 15% at Ascension level 10.
The stats for upgrading the Plus version of this armor are unknown at this time, but the maxed stats are 4362/3910.