A 2-mana white flash Elf from Lorwyn Eclipsed that hands another creature persist at instant speed — the cheapest way to give a value or combat creature a free extra death.
ETB value decks. Flashing Rhys in to grant persist to a creature about to die retriggers its enter-the-battlefield ability for free, turning a loss into extra value.
Combat protection. Cast at instant speed in response to a removal spell or a bad block, persist lets the targeted creature come right back rather than staying dead.
Counters matter decks. The activated ability to strip counters doubles as a way to clean up -1/-1 counters from persist itself or from opposing effects.
How it does in Commander
As the commander
It's a fine budget commander for a white Elf or counters-focused deck, but its low-impact stats and single-use trigger make it a more natural fit as a support piece in someone else's 99 than a deck's central plan.
In the 99
A cheap, flexible protection and value piece in any white deck running strong ETB creatures — flash lets it react to combat and removal rather than only being useful on your own turn.
Formats it's strong in
ETB value and blink-adjacent decks. Persist retriggers an enter-the-battlefield ability the same way a blink effect does, for a fraction of the mana investment.
Decks facing a lot of removal. Flashing Rhys in as a response to targeted removal turns a two-for-one against you into a wash or better.
Formats it's weak in
Decks with few valuable ETB creatures. Without something worth retriggering, granting persist is a minor combat trick at best.
Fast, low-interaction pods. A cheap protection trick is a small effect at a table where the game is often decided before combat tricks matter much.
Synergistic cards
Solemn Simulacrum — A classic ETB value creature that becomes a repeatable draw-and-ramp engine the moment persist lets it die and come back.
Reveillark — Another strong ETB creature that gets extra mileage from a free additional death and return.
Kitchen Finks — Already has persist itself, but the deck shape this card wants — small value creatures with death triggers — is the same one Rhys supports.
Any cheap sacrifice outlet — Sacrificing a creature Rhys has just given persist to is a guaranteed way to retrigger its ETB on your own terms.
Is it worth the price?
As a recent-set card, Rhys, the Evermore is inexpensive and worth a slot in any white deck already running strong ETB creatures — low cost for a real piece of interaction.