The Sylas build for Mid is Lich Bane, Zhonya's Hourglass, and Rod of Ages. This LoL Sylas guide for Mid at Platinum+ on 14.3 includes runes, items, skill order, and counters.
Sylas Counters
52.3%
(-0.4%)
49.7%
(+0.2%)
10.9%
19.6%
(-2.0%)
822
(+12)