Arcbound Ravager is the most complicated card in Affinity
It's likely to catch removal, but if it sticks you'll have a rapidly growing flier that makes your opponents sacrifice a nonland permanent with every attack
A 3-mana removal spell is decent, but again, offering that or an untapped land makes it very powerful
I've faced it several times, but never survived enough to see the Mega Flare just obliterate a table
Primeval Titan is the main win condition for Amulet Titan by representing a large attacker and a tutor for various lands, including the combo finisher of Valakut, the Molten Pinnacle in combination with Dryad of the Ilysian Grove
To answer the first question, Lorehold is a hasty, flying 5/5 dragon for five mana (one of which must be red, and one of which must be white)