Metastasio's Hat

Metastasio's Hat is a alchemical cloth minor hat. It's an article of clothing, worn on the head. "Metastasio envisioned whole armies that would lob grenades at the enemy, and he designed this hat to help soldiers succeed. When worn, it decreases the chance that grenades get thrown back at you by 15%." Metastasio's Hat has no cursed variant.

Strategy
Since this item has no cursed variant, you don't need to worry about its effects changing after wearing it. For reference, the chance of a grenade being thrown back at the player is as follows:


 * 0% chance if there's nobody in the room capable of throwing the grenade back at the player, otherwise:
 * 25% + (5% * the amount of living rogues in a room that are capable of throwing the grenade back)
 * - 20% if throwing the grenade to a room downwards of yours.
 * + 20% if throwing the grenade to a room upwards of yours.
 * - 15% if wearing Metastasio's Hat

A couple of relevant conclusions we can draw from the statistics above:


 * The chance of a grenade being thrown back at the player when throwing the grenade in a cardinal direction against a single, living, capable rogue is halved (becoming 15% as opposed to 30%).
 * ((25% base) + (5% * 1 rogue) = 30%) - (15% from wearing Metastasio's Hat) = 15%
 * Throwing a grenade downwards carries no risk of it being thrown back at the player if there are two or less rogues in the room.
 * ((25% base) + (5% * 2 rogues = 10%) = 35%)) - (20% throwing the grenade downwards) - (15% from wearing Metastasio's Hat) = 0%

Overall, this makes using grenades much more viable than they are normally, but some level of caution should still be exerted in most cases nonetheless.