It could be Athena on the reverse, maybe not Ares: https://www.wildwinds.com/coins/ric/macrinus/_markianopolis_Moushmov_537.jpg
Here's my specimen: Macrinus and Diadumenian, AD 217-218. Roman provincial Æ Pentassarion, 12.06 g, 26.5 mm, 6 h. Moesia Inferior, Marcianopolis, Legate Pontius Furius Pontianus, June/Aug 217-Nov/Dec 217. Obv: ΑΝΤ Κ ΟΠΕΛ CΕV ΜΑΚΡΕΙΝΟC Κ Μ ΟΠΕ ΑΝΤΩΝΕΙΝΟC, Confronted heads of Macrinus right, laureate, and Diadumenian left, bare. Rev: VΠ ΠΟΝΤΙΑΝΟV ΜΑΡΚΙΑΝΟΠΟΛΙΤΩΝ, Athena wearing helmet and aegis, standing left, holding owl and inverted spear; E in right field. Refs: AMNG I 734v.; Hristova & Jekov 6.24.4.7; Varbanov 1170a; BMC 30v.; Moushmov 537; Wiczay 2148v.
MACRINUS and is with Son Diadumenian RI Didumenian and Macrinus 217-218 CE AE28 Markianopolis mint Serapis