This is pretty cool, a nice way for people to have another chance at those Powerslave Awakening Shards, without having to go too far out of their way.
Blue Minotaur is pretty quick for the shield one, and people have already suggested Alchemy Talis for Invincibility.
Keep in mind there are still 4 days remaining if you've not done the 500 Frontier Dungeon runs with Ascension Talismans either. As long as Frontier Dungeons count as Time Rift Dungeons, good room for some overlap.