歐西里斯的天空龍（オシリスの天空竜，Oshirisu no Tenkūryū，Slifer the Sky Dragon）是《遊戲王》中的三幻神之一，由武藤遊戲在動畫與漫畫中持有。這張卡在故事中被設定為極強的存在，擁有神話級的力量與威嚴。它的設計靈感來自埃及神話中的歐西里斯（Osiris），並擁有獨特的雙頭龍外觀，象徵著無上的力量與審判。

能力與優勢
歐西里斯的天空龍的最大特點是它的攻擊力與防禦力與持有者手牌的數量直接掛鉤，每張手牌可提供1000攻擊與防禦點數。這使它的數值極具彈性，在擁有大量手牌時可以輕易超越其他怪獸的攻擊力。此特性讓玩家可以透過特定戰術，如「手牌補充」效果來迅速強化它的戰鬥力。另一個強大的效果是「召喚神之雷」（召雷彈），當對手召喚、反轉召喚或特殊召喚怪獸時，該怪獸的攻擊力或防禦力將立即下降2000點，若此數值降至0則該怪獸直接被破壞。這使得歐西里斯能夠有效壓制對手的場面，尤其針對低星級或依靠特殊召喚的卡組來說，這個能力是毀滅性的。此外，作為三幻神之一，它擁有「神的特殊抗性」，無法成為對手的效果目標，也不會被戰鬥或效果破壞（但仍受特定效果影響，如「球體模式」或「冥界的魔王 哈帝斯」的效果）。

弱點與劣勢
儘管歐西里斯的天空龍擁有強大的戰場控制能力，但它的發揮依賴於手牌數量，因此若玩家的手牌不足，其攻擊與防禦力也會變得相當低，容易遭受對手攻擊。此外，它的召喚條件嚴格，需要三體祭品才能進行通常召喚，這在快節奏的環境中可能會讓玩家難以迅速展開戰術。另一個主要缺點是它無法對應「非目標但能影響全場」的效果，如「技能抽取」會使其效果無效，或「拉之翼神龍-球體模式」可以直接將其解決。此外，由於它的能力與手牌數量息息相關，一旦遭受「手牌破壞」類卡片攻擊，如「強制脫出裝置」或「雷擊」，其戰鬥力將大幅下降。

整體而言，歐西里斯的天空龍是一張攻防兼具的強力怪獸，適合與高手牌補充能力的卡組搭配發揮最大效果。然而，由於召喚條件與對手可能採取的針對手段，玩家在使用時仍需謹慎考量戰術，以發揮它真正的威力。

Slifer the Sky Dragon (オシリスの天空竜, Oshirisu no Tenkūryū) is one of the three Egyptian God Cards in Yu-Gi-Oh!, owned by Yugi Mutou in both the anime and manga. This card is depicted as an incredibly powerful entity, possessing mythological strength and majesty. Its design is inspired by Osiris from Egyptian mythology and features a distinctive two-headed dragon appearance, symbolizing supreme power and judgment.

Abilities and Strengths

Slifer the Sky Dragon's most notable trait is that its ATK and DEF are directly linked to the number of cards in its controller’s hand, gaining 1000 ATK and DEF for each card. This makes its stats highly flexible, allowing it to easily surpass other monsters in power when the player has a large hand. This unique mechanic enables players to enhance Slifer’s strength through strategies focused on hand replenishment effects.

Another powerful effect is its Thunder Force, which activates whenever an opponent summons, flip summons, or special summons a monster. That monster’s ATK or DEF is immediately reduced by 2000 points, and if it drops to 0, it is destroyed. This gives Slifer strong field control, especially against low-level monsters or decks that rely on special summons, making this effect particularly devastating.

Additionally, as one of the three Egyptian God Cards, Slifer possesses divine protection, meaning it cannot be targeted by the opponent’s effects and is immune to destruction by battle or effects. However, it is still vulnerable to specific effects such as The Winged Dragon of Ra - Sphere Mode or Dark Ruler Ha Des.

Weaknesses and Drawbacks

Despite its formidable battlefield control, Slifer’s effectiveness depends heavily on the number of cards in the player’s hand. If the player has a low hand count, its ATK and DEF will also be significantly reduced, making it vulnerable to enemy attacks. Furthermore, its summoning condition is demanding, requiring three tributes for a normal summon, which can slow down strategies in fast-paced duels.

Another major weakness is its vulnerability to effects that do not target but still affect the entire field. For example, Skill Drain can nullify its effect, and The Winged Dragon of Ra - Sphere Mode can remove it from the field outright. Since its power is directly tied to the number of cards in hand, it is also susceptible to hand destruction effects, such as Compulsory Evacuation Device or Raigeki, which can severely weaken it.

Overall, Slifer the Sky Dragon is a powerful monster with both offensive and defensive capabilities, best utilized in decks that emphasize hand advantage. However, due to its strict summoning requirements and potential counterplay options available to opponents, players must carefully plan their strategies to maximize its true potential.