In a fun turn of events, it seems like Grixis upkeeps is a lot more of an enchantment deck than I expected, so here are some all-stars that work great in both Obeka and The Ninth Doctor
And consider whether the benefits outweigh them
This only works with Obosh as your Commander or in the 99
(There is also a neutral color used by artifacts, well come back to that.) Each color has a theme long established: White: Peace, law, structure, selflessness, equality Blue: Knowledge, deceit, caution, deliberation, perfection Black: Power, self-interest, death, sacrifice, uninhibitedness Red: Freedom, emotion, action, impulse, destruction Green: Nature, wildlife, connection, spirituality, tradition (From the Color page of the MtG Fandom wiki.) Colors form a complex structure of alliances and enmities based on their relative positions in the color pie: for example, white is adjacent to blue and green in the wheel, and opposite to red and black
These can each exist on the battlefield without the legend rule kicking in
Cards like Archangel of Thune and Heliod, Sun-Crowned can provide extra counters to make this cost less steep