Land cycle looks sweet. They all look like easy includes in monocolor decks, and likely includes in two color decks as well. Beyond that, depends on what your manabase looks like - one land of a basic land type is trivial for green decks and decks with fetch/shock manabases, but can be more difficult for others. If you expect the lands to enter tapped, the cost of running them goes up significantly.
The lands all remind me of the Alliances cycle of lands -
Kjeldoran Outpost and
Soldevi Excavations in particular, although the newer cards do look much better due to not needing the land sacrifice.
As for the individual cards...
Castle Ardenvale is a bit expensive. I'm not sure if I like it more than
Westvale Abbey. Lower opportunity cost means it is probably better, but I suppose it depends how much you care about Ormendahl.
Castle Vantress is a reasonable lategame mana sink. Definitely want to throw it in Thada.
Castle Locthwain is repeatable card advantage on a land, which is always worth consideration. That can be a hefty life loss, but if you only expect to activate it when you're out of cards (ex: in a
Malfegor deck), it's pretty trivial to pay.
Castle Embereth is, to me, the least impressive of the bunch, but pump for a go-wide deck is good. I could see it in
Krenko, Mob Boss and similar decks.
Castle Garenbrig is
Temple of the False God-ish. Only provides mana for creature spells, but free ramp is free ramp. Limiting it to only creatures and abilities of creatures does limit it though.
As for other cards...
Realm-Cloaked Giant looks fine. Easy include in giant tribal decks. I don't think the giant beater makes it worth playing over other wraths-with-upside, but it's not a bad option to have.
Acclaimed Contender is good if you expect to trigger it consistently, but obviously limited to tribal decks.
Escape to the Wilds looks quite good. I'm usually not a big fan of the impulsive draw spells, but five cards for five mana is a really good deal, and the extra land drop makes it more likely for you to play all of them.