April 1, 1234: Richard Marshal channeled the cthonic powers to fend off 140 knights with only 15. He eventually surrendered the field of the Battle of the Curragh, and on 16 April succumbed to the toll of being a gateway for such fell power.
April 2, 1912: The RMS Titanic put to sea for its first trials. They offended a selkie off the Shetland coast, and if the captain had logged it instead of indulging his pride, they might have shed the curse before that fateful iceberg.
April 3, 1975: Chess grandmaster Bobby Fischer forfeits his title, too drained by his constant internal battle with the demon of order striving to possess his body.
April 4, 1875: The premiere of Bedřich Smetana's Vltava caused—or at least correlated with—the spontaneous erupture of several pure water springs across Bohemia.
April 5, 1879: Chile declared war on Bolivia and Peru, having secured promises of assistance from the magmars of the Peru-Chile Trench.
April 6, 1580: The bound god Sûl struggled beneath the Dover Straits, causing the most severe recorded earthquake in the region.
April 7, 1767: The Burmese army tore down the walls of Ayutthaya, sacked the city, and committed unspeakable atrocities. Commander Ne Myo Thihapate tore the city apart seeking a mysterious spirit that could grant him a wish, which he never found.
April 8, 1820: Yorgos, Antonio, and Theodoros invoked elder powers to bind a deity on the island Milos. The spell unseated their minds, making their identities uncertain even to them, and leaving the deity trapped in a statue now called the Venus de Milo.
April 9, 1937: The first Japanese-built aircraft to fly from Japan to Europe landed in London. The Kamikaze-go was the result of esoteric research incorporating auto-propitiation of little gods into the engine to achieve long-distance flight.
April 10, 837: The extradimensional space traveler known locally as Halley's Comet made its closest approach to Earth. It's been trying to get farther away ever since.
April 11, 1962: Former Olympic gold medalist George Poage accepted a position as educator and orator in neighboring otherworld Amnok. Terms of his employment mean he won't return until at least 2062.
April 12, 240: Shapur I joined his father Ardashir I as co-emperor if the Sasanian Empire. After two years, their patron spirit Mazda had merged their minds and spirits, and they/he could release the Ardashir body into death.
April 13, 1976: The US Treasury reissued the $2 bill as a Federal Reserve Note, which has been in print since then. For every hundred such bills issued, one $2 bill from the United States Note period (1862-1966) mysterious vanished, increasing their value.
April 14, 2003: The Human Genome Project completed the mapping of 99% of the human genome to 99.99% accuracy. Those aliens supervising the Earth experiment then concluded the study, declaring it "unsalvageably spoiled," and left for parts unknown.
April 15, 1907: Students at the University of Illinois founded the Triangle Fraternity, one of three national fraternities not named in Greek letters and therefore free of the Hellenic Bindings that allow ancient Greek liches influence over members' minds.
April 16, 2012: The Pulitzer Prize Board awarded the fiction prize to Untitled Dragons by Irmga Vorsla from a different reality. As in the other ten times this happened, they announced no winner to conceal the truth from reality locals.
April 17, 2014: The public officially learned of Kepler-186f, the first exoplanet in another star's habitable zone. NASA delayed the announcement for several years for their extrasolar colleagues, who wanted to launch their colony ship first.
April 18, 1917: Vladimir Petrovich Serbsky entered a patient's mind to battle their inner demons, as he had thousands of times before. He did not return. The patient recovered, and some theorize he still hops from mind to mind, healing the wounded.
April 19, 1770: A 14-year-old Marie Antoinette married the Dauphin of France in Vienna. Due to scheduling conflicts, groom Louis-Auguste had to remotely possess Marie's brother Ferdinand to complete the ceremony. They met in person 25 days later.
April 20, 1535: A collection of sun ghosts, called sun dogs, cavorted in the sky over Stockholm. Urban målare captured some of their power in the painting Vädersolstavlan, holding them in Sweden's service until the painting's loss in the 1600s.
April 21, 1821: Benderli Ali Pasha arrived in Constantinople to take up his authority as Grand Vizier of the Ottoman Empire. The position drew on his energy to maintain imperial magic, draining him over only nine days.
April 22, 1864: The Coinage Act of 1864 placed, for the first time, the phrase "In God We Trust" on United States coinage, thenceforth binding the nation's spiritual energy (including that available for incorporeal beings to siphon) to its economy.
April 23, 1959: The entity known as Unity Dow won a debate of worthiness, permitting her to enter the world as a birthing infant.
April 24, 1913: The Woolworth Building opened for the first time, Originally "borrowed" colocationally from an adjacent, more-advanced dimension, the presence of visitors, and then tenants, cemented it into our dimension.
April 25, 1607: The Sunken Ones held the Spanish fleet anchored in the Bay of Gibralter while the Dutch fleet overwhelmed them. Before day's end, the Sunken Ones took Dutch commander Jacob van Heemskerk to their realm in payment.
April 26, 1721: A jealous sorcerer caused a massive earthquake in Tabriz when she learned an alchemist was on the verge of discovering a form of immortality. Six years later, the scholar's research once more neared fruition and she did it again.
April 27, 1521: Ferdinand Magellan died, struck down by Philippine natives rather than be converted. Ferdinand was subtly betrayed and undermined by the small god Lismak, who wagered that Magellen could not circumnavigate the globe and did not want to lose.
April 28, 1402: A lesser god of the Mexica embodied itself in Nezahualcoyotl, who would go on to build an empty temple where, contrary to the dominant culture, he permitted no blood sacrifices.
April 29, 1911: Beijing founded Tsinghua College as required by the Boxer Protocol, using a tutelary spirit imported from the United States as the founding genius locus for the university's studies.
April 30, 1948: The Organization of American States formed from among those nations capable of using the American continents' arcanological teleportation system.