Direct answer: the Second Church of Marika is in central Altus Plateau, reached by following the road north from the Altus Highway Junction. It contains no Bell Bearing and no Haligtree Medallion. What it does contain is the end of the Bloody Finger Hunter Yura questline and the Eleonora’s Poleblade, which is one of the better early-game DEX weapons in the game.
A correction worth stating plainly
If you came here looking for a Bell Bearing or a Haligtree Medallion half, this is the wrong church and neither item is here. The four Churches of Marika are easy to confuse, and the medallion halves in particular are widely misattributed. The Haligtree Secret Medallion (Right) comes from Old Albus, who is disguised as a pot in southern Liurnia — hit the pot to break the disguise and speak to him. The Left half is on the roof of the tower in the north-east of Castle Sol, only reachable after defeating Commander Niall in the Mountaintops of the Giants. Neither is in Altus, and neither is at this church.
Both halves together activate the Grand Lift of Rold and open the path to the Consecrated Snowfield. If you have the right half, the left half is the only thing standing between you and that region.
What the church actually is
It is the final location of Yura’s questline, and the church is only interesting if you have already advanced him far enough. If you helped him in Limgrave and again in Liurnia, he retreats here and you can speak to him before he dies. The encounter is time-sensitive: attack him at the right moment and Eleonora, Violet Bloody Finger invades the church, dropping Eleonora’s Poleblade and the Purifying Crystal Tear.
Get the timing wrong and you kill Yura with nothing to show for it. This is the single most commonly fumbled quest step in the early game, so it is worth doing deliberately rather than wandering in and swinging.
Inside the church you will also find a Sacred Tear on a corpse, and a Lesser Sanguine Noble guarding the altar area. The Sanguine Noble is the regular occupant before or after Yura’s event — the Lesser version is an unusually aggressive one for a starting enemy, and it hits hard relative to what you will have at that point.
About Eleonora’s Poleblade
It is a thrusting sword with good scaling and high critical hit value, and it infuses itself with blood loss on a critical. It is a genuinely strong option if you have invested in dexterity, and the skill it carries, Eochaid’s Dancing Blade, is one of the better weapon skills in the game for a Dexterity build. Both rewards from the invasion are worth the setup.
Evidence status
Research-reviewed. The church’s location, its contents, the Yura quest event, the Eleonora invasion rewards, and the true locations of both Haligtree Medallion halves were each cross-checked against multiple independent references. The claim that this church holds a Bell Bearing or a medallion half was checked and rejected rather than published. This guide has not been play-tested on camera.