You wont trigger effects like whenever you cast a dragon spell when you cast an omen
To the niche and tribal cards from fringe and Commander decks that have been around for what feels like forever: Ryan Pancoasts Master of the Pearl Trident, Eric Fortunes Mulldrifter, and even Jesper Ejsings Fblthp, the Lost
The effects are: Move the target 6" Drop a Scheme Marker touching the target If enemy, make the target Craven
Europe had a LAN event for their Aeos Cup series at European International Championships
Hexproof was introduced in part because it makes more sense intuitively to cast spells to strengthen the creatures you summon instead of being unable to do so because of their aversion to magic
The Mystic gets a bit better with enchantments that want to be sacrificed, like Seal of Cleansing or even Hyena Umbra, but you're really running this for the cost reduction and the rest is bonus