Ring of Evos Isle is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

: Equipped creature gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.) At the beginning of your upkeep, put a +1/+1 counter on equipped creature if it's blue. Equip (: Attach to target creature you control. Equip only as a sorcery.)