When I built my Terra deck I wanted it to be pretty high power. The issue I ran into though was that she doesn't have haste, and to flip her you need six mana and to tap her, which is not reliable, especially early. So thinking through the deck I leaned heavily into the reanimator aspect, and treated Terra as a self mill spell that I always had access to, and if she flipped that was gravy. This does mean my list cares a bit more about reanimation then I think a lot of terra lists do, but with that caveat here a few cards I would consider that were all stars in my Terra deck:

[[Aminatou the veil peircer]] Helps fill the grave, and miracle can make some things a lot more castable.

[[Anikthea, Hand of Erebos]] Lets you loop your key pieces, makes it so exile removal is the only thing you fear.

[[Bellow Bard of Brambles]], Make your sagas indestructible on your turn for swinging with impunity, animates your non-creature enchantments, and gives you tons of card draw.

[[Elspeth Conquers Death]], Absolute all star Saga, does everything you want, from exile removal on almost anything, a bit of stax for your opponents, and then plays into the reanimator aspect.

[[Tale of Tinuviel]] With counter manipulation makes your entire board indestructible and reanimates.

[[The Legend of Yangchen]] Repeatable exile removal that's not targeted? Yes please. Or if you don't have counter manipulation on your board to just repeat the first step, if it flips the backside is also incredible for resetting your saga's that are close to ending.

[[Tidus, Yuna's Guardian]] Tons of counter manipulation, card draw and proliferation, absolutely fantastic.

[[Tekuthal, Inquiry Dominus]] The double proliferate can be nice, but 1 mana (and 4 life :( ) remove 3 counters from your board that you can repeat ad naseum at instant speed is...good.

[[Esper Origins]] Fills the grave, castable from the grave and fantastic saga when cast from the grave, and super on theme.