Shield Bash is a Skill in Elden Ring. Shield Bash is a regular skill that can be use by equipping the some Greatshields. Updated to Patch 1.08

Elden Ring Shield Bash Guide, Notes & Tips

• This is an Ash of War Skill, associated with the Ash of War: Shield Bash.
• FP Cost: 10
• This Skill is not Chargeable
• This skill's move is the same regardless of if the FP requirement is met; the differences between a non-FP and FP-charged Shield Bash appear to be that the former deals roughly 50% of the latter, and does not deal as much stance damage, thus not knocking down enemies as readily and breaking their poise
• Like most Skills, the full FP requirement must be met at the time of casting to perform the FP-charged ability. Regardless of if it is successfully performed or the FP-less version is done instead, FP will be drained (e.g. FP cost of 10, player has 9 FP, uses Skill, the result is the player will perform the weaker FP-less version and have their FP drained to 0).
• When combined with Talismans such as the Carian Filigreed Crest and the Ancestral Spirit's Horn, a Shield Bash-focused playstyle becomes possible even on builds that have very little FP. By using a Greatshield with 100 PHY guard and high enough elemental guard, as well as decent offensive capability (such as the Spiked Palisade, or the Dragonclaw Shield) a player could hypothetically invest almost all levels and other stat-influencing items into maximising their stamina via putting points into Endurance, such that they could block most every physical attack with little risk and retaliate using guard counters and Shield Bashes, as well as keeping their equipment load maximum high enough that high-poise armour such as Lionel's Set, which helps to accommodate for Greatshields' slow attack rate and large window of vulnerability when attacking, can be equipped without exceeding a medium load, allowing for optimal dodge-rolling in addition to the already powerful defenses described.
• Regardless of how much Stamina the player has, so long as they use Shield Bash at the right time, they can block any and all attacks within the frames of the move. This is ideal as a way to tank a hit after attacking with a weapon to near zero stamina.
• NOTE: This Skill was changed with Patch 1.07 as follows: Stamina attack power against guarded enemies has been increased. 
• NOTE: As of Patch 1.08 the time it takes to activate the guard part of the Shield Bash Weapon Art has been reduced.