Syvarris is a ranged attack expert.
He has the longest range in the game, and can attack several times per turn.
Unfortunately, he is hampered by his low defense value.
Syvarris must be used with great care, as he is easy pickings for other ranged units.
Deploying him on a cliff is almost certainly suicide, as other figures will pick him off.
It would only be advisible if you could have him leap down behind the cliff for cover after shooting for a turn or two.
I generally try to deploy Syvarris out in the middle of knowwhere.
He tries to pick off enemy units that wander into his range.
If you don't use him early on, your opponent may kind of forget about him.
He may even make some tactical mistakes by moving important units into Syvarris' range.
This lets you mount a 'big' attack with him mid game.