Enchant creature
Enchanted creature gets +2/+2 and has protection from each color. This effect doesn't remove Auras. (It can't be blocked, targeted, or dealt damage by anything that's white, blue, black, red, or green.)
Hyena UmbraprotectionBudget$0.33Provides creature protection in white by granting first strike and totem armor, making the enchanted creature much harder to remove while still being an Aura-based upgrade path.
Ethereal ArmorprotectionBudget$1.14A white Aura that boosts a creature with a low mana cost and is commonly used to make a single threat much harder to answer by stacking enchantment-based defenses.
All That GlittersfinisherBudget$0.33Similar in that it turns one creature into a major threat through an Aura-like enchantment, though it focuses on power/toughness scaling rather than protection.
Indestructibilityprotection$1.70A white enchantment that provides strong defensive protection to a permanent, serving a similar role of making a key creature extremely difficult to remove.
Shielded by Faithprotection$4.72An Aura in white that makes a creature much harder to kill by granting indestructible, closely matching the protective function of Spectra Ward.
Unquestioned Authorityprotection$1.79Another white Aura that enhances a creature and grants protection-like evasion, helping a single creature punch through blockers while improving resilience.
Spirit Mantleprotection$3.04Very close functional analogue: a white Aura that gives the creature protection from creatures, effectively making it unblockable and harder to interact with combat-wise.
Unflinching CourageprotectionBudget$0.17A white Aura that increases a creature's combat dominance and survivability through a similar one-creature buff role, though it adds lifelink/trample instead of color protection.