These serve to keep Valgavoth in play as long as possible, and I feel are essential to a strong build
Magic's best white sorcery, Balance is one of the most unfair effects, and here lies its power
Think about if you have 10 creatures out, 3 of which have life drain effects
Of course, this is made easier by the fact that each deck contains a Sol Ring (#1 card in Commander) and a Commander's Sphere (#3 card in Commander), but Open Hostility gets both Skullclamp and Lightning Greaves, which rank in the top 20 cards in Commander
I also like countermagic in this archetype, as you can develop your fliers early then protect them or stop bombs later
Trample and haste are two of the most important keywords in equipment decks, second only to hexproof and flying/unblockable