Youll lose your lands too, thats true, but if youre already winning, you dont need your lands anymore
You will gain life equal to the sacrificed creatures toughness
I think if there are only, say, five or ten cards that use a mechanic, then its easier to just cut that mechanic

Sort Card Type Magmortar #12Holo Rare $7.24 Magmortar #31Rare $1.04 Magmortar #6Holo Rare $11.84 Magmortar #2Holo Rare $6.23 Magmortar #27Rare $1.20 Magmortar #16Holo Rare $7.37 Magmortar #21Rare $0.87 Magmortar #11Rare $0.48 Magmortar #19Holo Rare $0.60 Magmortar #22Rare $0.27 Magmortar #30Rare $0.28 Magmortar #20Rare $0.17 Magmortar #GG3Ultra Rare $11.51 Magmortar #10Rare $0.12 Magmortar #21Rare $0.15 Magmortar #14Rare $0.20 Magmortar #17Uncommon $0.34 Magmortar #15Uncommon $0.40 Magmortar #3Uncommon $0.57 Magmortar #16Rare $1.36 Magmortar #11Uncommon $1.95 Magmortar - 017/172 #17None $0.16 Magmortar - 175/172 #175Art Rare $4.79 Magmortar - 2/95 (Cracked Ice Holo) #2Promo $25.00 Magmortar - 31/132 (Secret Wonders) #31Holo Rare $2.29 Magmortar - DP20 #DP20Promo $16.39 Magmortar Lv.X #123Ultra Rare $66.41 Magmortar Lv.X #123Ultra Rare $66.41 Magmortar - 2/95 (Cracked Ice Holo) #2Promo $25.00 Magmortar - DP20 #DP20Promo $16.39 Magmortar #6Holo Rare $11.84 Magmortar #GG3Ultra Rare $11.51 Magmortar #16Holo Rare $7.37 Magmortar #12Holo Rare $7.24 Magmortar #2Holo Rare $6.23 Magmortar - 175/172 #175Art Rare $4.79 Magmortar - 31/132 (Secret Wonders) #31Holo Rare $2.29

Apparently when you add a mana to Monastery Swiftspear, you get flying and an additional toughness
With a strength of 1 and willpower of 3 , Robin Hood can deal some sneaky blows to the opponents board with his Skirmish ability Exert this card to be able to deal 1 damage to chosen character